Update dependencies (legacy and go.mod)

37 files changed, 1946 insertions, 754 deletions

diff --git a/vendor/github.com/PuerkitoBio/goquery/README.md b/vendor/github.com/PuerkitoBio/goquery/README.md
index 84f9af3..c9db736 100644
--- a/vendor/github.com/PuerkitoBio/goquery/README.md
+++ b/vendor/github.com/PuerkitoBio/goquery/README.md
@@ -138,9 +138,11 @@ func main() {
 - [Goq][goq], an HTML deserialization and scraping library based on goquery and struct tags.
 - [andybalholm/cascadia][cascadia], the CSS selector library used by goquery.
 - [suntong/cascadia][cascadiacli], a command-line interface to the cascadia CSS selector library, useful to test selectors.
-- [asciimoo/colly](https://github.com/asciimoo/colly), a lightning fast and elegant Scraping Framework
+- [gocolly/colly](https://github.com/gocolly/colly), a lightning fast and elegant Scraping Framework
 - [gnulnx/goperf](https://github.com/gnulnx/goperf), a website performance test tool that also fetches static assets.
 - [MontFerret/ferret](https://github.com/MontFerret/ferret), declarative web scraping.
+- [tacusci/berrycms](https://github.com/tacusci/berrycms), a modern simple to use CMS with easy to write plugins
+- [Dataflow kit](https://github.com/slotix/dataflowkit), Web Scraping framework for Gophers.  
 
 ## Support
 
diff --git a/vendor/github.com/andybalholm/cascadia/parser.go b/vendor/github.com/andybalholm/cascadia/parser.go
index 495db9c..bebf0af 100644
--- a/vendor/github.com/andybalholm/cascadia/parser.go
+++ b/vendor/github.com/andybalholm/cascadia/parser.go
@@ -7,14 +7,16 @@ import (
 	"regexp"
 	"strconv"
 	"strings"
-
-	"golang.org/x/net/html"
 )
 
 // a parser for CSS selectors
 type parser struct {
 	s string // the source text
 	i int    // the current position
+
+	// if `false`, parsing a pseudo-element
+	// returns an error.
+	acceptPseudoElements bool
 }
 
 // parseEscape parses a backslash escape.
@@ -56,6 +58,26 @@ func (p *parser) parseEscape() (result string, err error) {
 	return result, nil
 }
 
+// toLowerASCII returns s with all ASCII capital letters lowercased.
+func toLowerASCII(s string) string {
+	var b []byte
+	for i := 0; i < len(s); i++ {
+		if c := s[i]; 'A' <= c && c <= 'Z' {
+			if b == nil {
+				b = make([]byte, len(s))
+				copy(b, s)
+			}
+			b[i] = s[i] + ('a' - 'A')
+		}
+	}
+
+	if b == nil {
+		return s
+	}
+
+	return string(b)
+}
+
 func hexDigit(c byte) bool {
 	return '0' <= c && c <= '9' || 'a' <= c && c <= 'f' || 'A' <= c && c <= 'F'
 }
@@ -280,92 +302,92 @@ func (p *parser) consumeClosingParenthesis() bool {
 }
 
 // parseTypeSelector parses a type selector (one that matches by tag name).
-func (p *parser) parseTypeSelector() (result Selector, err error) {
+func (p *parser) parseTypeSelector() (result tagSelector, err error) {
 	tag, err := p.parseIdentifier()
 	if err != nil {
-		return nil, err
+		return
 	}
-
-	return typeSelector(tag), nil
+	return tagSelector{tag: toLowerASCII(tag)}, nil
 }
 
 // parseIDSelector parses a selector that matches by id attribute.
-func (p *parser) parseIDSelector() (Selector, error) {
+func (p *parser) parseIDSelector() (idSelector, error) {
 	if p.i >= len(p.s) {
-		return nil, fmt.Errorf("expected id selector (#id), found EOF instead")
+		return idSelector{}, fmt.Errorf("expected id selector (#id), found EOF instead")
 	}
 	if p.s[p.i] != '#' {
-		return nil, fmt.Errorf("expected id selector (#id), found '%c' instead", p.s[p.i])
+		return idSelector{}, fmt.Errorf("expected id selector (#id), found '%c' instead", p.s[p.i])
 	}
 
 	p.i++
 	id, err := p.parseName()
 	if err != nil {
-		return nil, err
+		return idSelector{}, err
 	}
 
-	return attributeEqualsSelector("id", id), nil
+	return idSelector{id: id}, nil
 }
 
 // parseClassSelector parses a selector that matches by class attribute.
-func (p *parser) parseClassSelector() (Selector, error) {
+func (p *parser) parseClassSelector() (classSelector, error) {
 	if p.i >= len(p.s) {
-		return nil, fmt.Errorf("expected class selector (.class), found EOF instead")
+		return classSelector{}, fmt.Errorf("expected class selector (.class), found EOF instead")
 	}
 	if p.s[p.i] != '.' {
-		return nil, fmt.Errorf("expected class selector (.class), found '%c' instead", p.s[p.i])
+		return classSelector{}, fmt.Errorf("expected class selector (.class), found '%c' instead", p.s[p.i])
 	}
 
 	p.i++
 	class, err := p.parseIdentifier()
 	if err != nil {
-		return nil, err
+		return classSelector{}, err
 	}
 
-	return attributeIncludesSelector("class", class), nil
+	return classSelector{class: class}, nil
 }
 
 // parseAttributeSelector parses a selector that matches by attribute value.
-func (p *parser) parseAttributeSelector() (Selector, error) {
+func (p *parser) parseAttributeSelector() (attrSelector, error) {
 	if p.i >= len(p.s) {
-		return nil, fmt.Errorf("expected attribute selector ([attribute]), found EOF instead")
+		return attrSelector{}, fmt.Errorf("expected attribute selector ([attribute]), found EOF instead")
 	}
 	if p.s[p.i] != '[' {
-		return nil, fmt.Errorf("expected attribute selector ([attribute]), found '%c' instead", p.s[p.i])
+		return attrSelector{}, fmt.Errorf("expected attribute selector ([attribute]), found '%c' instead", p.s[p.i])
 	}
 
 	p.i++
 	p.skipWhitespace()
 	key, err := p.parseIdentifier()
 	if err != nil {
-		return nil, err
+		return attrSelector{}, err
 	}
+	key = toLowerASCII(key)
 
 	p.skipWhitespace()
 	if p.i >= len(p.s) {
-		return nil, errors.New("unexpected EOF in attribute selector")
+		return attrSelector{}, errors.New("unexpected EOF in attribute selector")
 	}
 
 	if p.s[p.i] == ']' {
 		p.i++
-		return attributeExistsSelector(key), nil
+		return attrSelector{key: key, operation: ""}, nil
 	}
 
 	if p.i+2 >= len(p.s) {
-		return nil, errors.New("unexpected EOF in attribute selector")
+		return attrSelector{}, errors.New("unexpected EOF in attribute selector")
 	}
 
 	op := p.s[p.i : p.i+2]
 	if op[0] == '=' {
 		op = "="
 	} else if op[1] != '=' {
-		return nil, fmt.Errorf(`expected equality operator, found "%s" instead`, op)
+		return attrSelector{}, fmt.Errorf(`expected equality operator, found "%s" instead`, op)
 	}
 	p.i += len(op)
 
 	p.skipWhitespace()
 	if p.i >= len(p.s) {
-		return nil, errors.New("unexpected EOF in attribute selector")
+		return attrSelector{}, errors.New("unexpected EOF in attribute selector")
 	}
 	var val string
 	var rx *regexp.Regexp
@@ -380,88 +402,84 @@ func (p *parser) parseAttributeSelector() (Selector, error) {
 		}
 	}
 	if err != nil {
-		return nil, err
+		return attrSelector{}, err
 	}
 
 	p.skipWhitespace()
 	if p.i >= len(p.s) {
-		return nil, errors.New("unexpected EOF in attribute selector")
+		return attrSelector{}, errors.New("unexpected EOF in attribute selector")
 	}
 	if p.s[p.i] != ']' {
-		return nil, fmt.Errorf("expected ']', found '%c' instead", p.s[p.i])
+		return attrSelector{}, fmt.Errorf("expected ']', found '%c' instead", p.s[p.i])
 	}
 	p.i++
 
 	switch op {
-	case "=":
-		return attributeEqualsSelector(key, val), nil
-	case "!=":
-		return attributeNotEqualSelector(key, val), nil
-	case "~=":
-		return attributeIncludesSelector(key, val), nil
-	case "|=":
-		return attributeDashmatchSelector(key, val), nil
-	case "^=":
-		return attributePrefixSelector(key, val), nil
-	case "$=":
-		return attributeSuffixSelector(key, val), nil
-	case "*=":
-		return attributeSubstringSelector(key, val), nil
-	case "#=":
-		return attributeRegexSelector(key, rx), nil
-	}
-
-	return nil, fmt.Errorf("attribute operator %q is not supported", op)
+	case "=", "!=", "~=", "|=", "^=", "$=", "*=", "#=":
+		return attrSelector{key: key, val: val, operation: op, regexp: rx}, nil
+	default:
+		return attrSelector{}, fmt.Errorf("attribute operator %q is not supported", op)
+	}
 }
 
 var errExpectedParenthesis = errors.New("expected '(' but didn't find it")
 var errExpectedClosingParenthesis = errors.New("expected ')' but didn't find it")
 var errUnmatchedParenthesis = errors.New("unmatched '('")
 
-// parsePseudoclassSelector parses a pseudoclass selector like :not(p).
-func (p *parser) parsePseudoclassSelector() (Selector, error) {
+// parsePseudoclassSelector parses a pseudoclass selector like :not(p) or a pseudo-element
+// For backwards compatibility, both ':' and '::' prefix are allowed for pseudo-elements.
+// https://drafts.csswg.org/selectors-3/#pseudo-elements
+// Returning a nil `Sel` (and a nil `error`) means we found a pseudo-element.
+func (p *parser) parsePseudoclassSelector() (out Sel, pseudoElement string, err error) {
 	if p.i >= len(p.s) {
-		return nil, fmt.Errorf("expected pseudoclass selector (:pseudoclass), found EOF instead")
+		return nil, "", fmt.Errorf("expected pseudoclass selector (:pseudoclass), found EOF instead")
 	}
 	if p.s[p.i] != ':' {
-		return nil, fmt.Errorf("expected attribute selector (:pseudoclass), found '%c' instead", p.s[p.i])
+		return nil, "", fmt.Errorf("expected attribute selector (:pseudoclass), found '%c' instead", p.s[p.i])
 	}
 
 	p.i++
+	var mustBePseudoElement bool
+	if p.i >= len(p.s) {
+		return nil, "", fmt.Errorf("got empty pseudoclass (or pseudoelement)")
+	}
+	if p.s[p.i] == ':' { // we found a pseudo-element
+		mustBePseudoElement = true
+		p.i++
+	}
+
 	name, err := p.parseIdentifier()
 	if err != nil {
-		return nil, err
+		return
 	}
 	name = toLowerASCII(name)
+	if mustBePseudoElement && (name != "after" && name != "backdrop" && name != "before" &&
+		name != "cue" && name != "first-letter" && name != "first-line" && name != "grammar-error" &&
+		name != "marker" && name != "placeholder" && name != "selection" && name != "spelling-error") {
+		return out, "", fmt.Errorf("unknown pseudoelement :%s", name)
+	}
 
 	switch name {
 	case "not", "has", "haschild":
 		if !p.consumeParenthesis() {
-			return nil, errExpectedParenthesis
+			return out, "", errExpectedParenthesis
 		}
 		sel, parseErr := p.parseSelectorGroup()
 		if parseErr != nil {
-			return nil, parseErr
+			return out, "", parseErr
 		}
 		if !p.consumeClosingParenthesis() {
-			return nil, errExpectedClosingParenthesis
+			return out, "", errExpectedClosingParenthesis
 		}
 
-		switch name {
-		case "not":
-			return negatedSelector(sel), nil
-		case "has":
-			return hasDescendantSelector(sel), nil
-		case "haschild":
-			return hasChildSelector(sel), nil
-		}
+		out = relativePseudoClassSelector{name: name, match: sel}
 
 	case "contains", "containsown":
 		if !p.consumeParenthesis() {
-			return nil, errExpectedParenthesis
+			return out, "", errExpectedParenthesis
 		}
 		if p.i == len(p.s) {
-			return nil, errUnmatchedParenthesis
+			return out, "", errUnmatchedParenthesis
 		}
 		var val string
 		switch p.s[p.i] {
@@ -471,95 +489,75 @@ func (p *parser) parsePseudoclassSelector() (Selector, error) {
 			val, err = p.parseIdentifier()
 		}
 		if err != nil {
-			return nil, err
+			return out, "", err
 		}
 		val = strings.ToLower(val)
 		p.skipWhitespace()
 		if p.i >= len(p.s) {
-			return nil, errors.New("unexpected EOF in pseudo selector")
+			return out, "", errors.New("unexpected EOF in pseudo selector")
 		}
 		if !p.consumeClosingParenthesis() {
-			return nil, errExpectedClosingParenthesis
+			return out, "", errExpectedClosingParenthesis
 		}
 
-		switch name {
-		case "contains":
-			return textSubstrSelector(val), nil
-		case "containsown":
-			return ownTextSubstrSelector(val), nil
-		}
+		out = containsPseudoClassSelector{own: name == "containsown", value: val}
 
 	case "matches", "matchesown":
 		if !p.consumeParenthesis() {
-			return nil, errExpectedParenthesis
+			return out, "", errExpectedParenthesis
 		}
 		rx, err := p.parseRegex()
 		if err != nil {
-			return nil, err
+			return out, "", err
 		}
 		if p.i >= len(p.s) {
-			return nil, errors.New("unexpected EOF in pseudo selector")
+			return out, "", errors.New("unexpected EOF in pseudo selector")
 		}
 		if !p.consumeClosingParenthesis() {
-			return nil, errExpectedClosingParenthesis
+			return out, "", errExpectedClosingParenthesis
 		}
 
-		switch name {
-		case "matches":
-			return textRegexSelector(rx), nil
-		case "matchesown":
-			return ownTextRegexSelector(rx), nil
-		}
+		out = regexpPseudoClassSelector{own: name == "matchesown", regexp: rx}
 
 	case "nth-child", "nth-last-child", "nth-of-type", "nth-last-of-type":
 		if !p.consumeParenthesis() {
-			return nil, errExpectedParenthesis
+			return out, "", errExpectedParenthesis
 		}
 		a, b, err := p.parseNth()
 		if err != nil {
-			return nil, err
+			return out, "", err
 		}
 		if !p.consumeClosingParenthesis() {
-			return nil, errExpectedClosingParenthesis
-		}
-		if a == 0 {
-			switch name {
-			case "nth-child":
-				return simpleNthChildSelector(b, false), nil
-			case "nth-of-type":
-				return simpleNthChildSelector(b, true), nil
-			case "nth-last-child":
-				return simpleNthLastChildSelector(b, false), nil
-			case "nth-last-of-type":
-				return simpleNthLastChildSelector(b, true), nil
-			}
+			return out, "", errExpectedClosingParenthesis
 		}
-		return nthChildSelector(a, b,
-				name == "nth-last-child" || name == "nth-last-of-type",
-				name == "nth-of-type" || name == "nth-last-of-type"),
-			nil
+		last := name == "nth-last-child" || name == "nth-last-of-type"
+		ofType := name == "nth-of-type" || name == "nth-last-of-type"
+		out = nthPseudoClassSelector{a: a, b: b, last: last, ofType: ofType}
 
 	case "first-child":
-		return simpleNthChildSelector(1, false), nil
+		out = nthPseudoClassSelector{a: 0, b: 1, ofType: false, last: false}
 	case "last-child":
-		return simpleNthLastChildSelector(1, false), nil
+		out = nthPseudoClassSelector{a: 0, b: 1, ofType: false, last: true}
 	case "first-of-type":
-		return simpleNthChildSelector(1, true), nil
+		out = nthPseudoClassSelector{a: 0, b: 1, ofType: true, last: false}
 	case "last-of-type":
-		return simpleNthLastChildSelector(1, true), nil
+		out = nthPseudoClassSelector{a: 0, b: 1, ofType: true, last: true}
 	case "only-child":
-		return onlyChildSelector(false), nil
+		out = onlyChildPseudoClassSelector{ofType: false}
 	case "only-of-type":
-		return onlyChildSelector(true), nil
+		out = onlyChildPseudoClassSelector{ofType: true}
 	case "input":
-		return inputSelector, nil
+		out = inputPseudoClassSelector{}
 	case "empty":
-		return emptyElementSelector, nil
+		out = emptyElementPseudoClassSelector{}
 	case "root":
-		return rootSelector, nil
+		out = rootPseudoClassSelector{}
+	case "after", "backdrop", "before", "cue", "first-letter", "first-line", "grammar-error", "marker", "placeholder", "selection", "spelling-error":
+		return nil, name, nil
+	default:
+		return out, "", fmt.Errorf("unknown pseudoclass or pseudoelement :%s", name)
 	}
-
-	return nil, fmt.Errorf("unknown pseudoclass :%s", name)
+	return
 }
 
 // parseInteger parses a  decimal integer.
@@ -705,8 +703,8 @@ invalid:
 
 // parseSimpleSelectorSequence parses a selector sequence that applies to
 // a single element.
-func (p *parser) parseSimpleSelectorSequence() (Selector, error) {
-	var result Selector
+func (p *parser) parseSimpleSelectorSequence() (Sel, error) {
+	var selectors []Sel
 
 	if p.i >= len(p.s) {
 		return nil, errors.New("expected selector, found EOF instead")
@@ -723,13 +721,17 @@ func (p *parser) parseSimpleSelectorSequence() (Selector, error) {
 		if err != nil {
 			return nil, err
 		}
-		result = r
+		selectors = append(selectors, r)
 	}
 
+	var pseudoElement string
 loop:
 	for p.i < len(p.s) {
-		var ns Selector
-		var err error
+		var (
+			ns               Sel
+			newPseudoElement string
+			err              error
+		)
 		switch p.s[p.i] {
 		case '#':
 			ns, err = p.parseIDSelector()
@@ -738,44 +740,57 @@ loop:
 		case '[':
 			ns, err = p.parseAttributeSelector()
 		case ':':
-			ns, err = p.parsePseudoclassSelector()
+			ns, newPseudoElement, err = p.parsePseudoclassSelector()
 		default:
 			break loop
 		}
 		if err != nil {
 			return nil, err
 		}
-		if result == nil {
-			result = ns
+		// From https://drafts.csswg.org/selectors-3/#pseudo-elements :
+		// "Only one pseudo-element may appear per selector, and if present
+		// it must appear after the sequence of simple selectors that
+		// represents the subjects of the selector.""
+		if ns == nil { // we found a pseudo-element
+			if pseudoElement != "" {
+				return nil, fmt.Errorf("only one pseudo-element is accepted per selector, got %s and %s", pseudoElement, newPseudoElement)
+			}
+			if !p.acceptPseudoElements {
+				return nil, fmt.Errorf("pseudo-element %s found, but pseudo-elements support is disabled", newPseudoElement)
+			}
+			pseudoElement = newPseudoElement
 		} else {
-			result = intersectionSelector(result, ns)
+			if pseudoElement != "" {
+				return nil, fmt.Errorf("pseudo-element %s must be at the end of selector", pseudoElement)
+			}
+			selectors = append(selectors, ns)
 		}
-	}
 
-	if result == nil {
-		result = func(n *html.Node) bool {
-			return n.Type == html.ElementNode
-		}
 	}
-
-	return result, nil
+	if len(selectors) == 1 && pseudoElement == "" { // no need wrap the selectors in compoundSelector
+		return selectors[0], nil
+	}
+	return compoundSelector{selectors: selectors, pseudoElement: pseudoElement}, nil
 }
 
 // parseSelector parses a selector that may include combinators.
-func (p *parser) parseSelector() (result Selector, err error) {
+func (p *parser) parseSelector() (Sel, error) {
 	p.skipWhitespace()
-	result, err = p.parseSimpleSelectorSequence()
+	result, err := p.parseSimpleSelectorSequence()
 	if err != nil {
-		return
+		return nil, err
 	}
 
 	for {
-		var combinator byte
+		var (
+			combinator byte
+			c          Sel
+		)
 		if p.skipWhitespace() {
 			combinator = ' '
 		}
 		if p.i >= len(p.s) {
-			return
+			return result, nil
 		}
 
 		switch p.s[p.i] {
@@ -785,51 +800,39 @@ func (p *parser) parseSelector() (result Selector, err error) {
 			p.skipWhitespace()
 		case ',', ')':
 			// These characters can't begin a selector, but they can legally occur after one.
-			return
+			return result, nil
 		}
 
 		if combinator == 0 {
-			return
+			return result, nil
 		}
 
-		c, err := p.parseSimpleSelectorSequence()
+		c, err = p.parseSimpleSelectorSequence()
 		if err != nil {
 			return nil, err
 		}
-
-		switch combinator {
-		case ' ':
-			result = descendantSelector(result, c)
-		case '>':
-			result = childSelector(result, c)
-		case '+':
-			result = siblingSelector(result, c, true)
-		case '~':
-			result = siblingSelector(result, c, false)
-		}
+		result = combinedSelector{first: result, combinator: combinator, second: c}
 	}
-
-	panic("unreachable")
 }
 
 // parseSelectorGroup parses a group of selectors, separated by commas.
-func (p *parser) parseSelectorGroup() (result Selector, err error) {
-	result, err = p.parseSelector()
+func (p *parser) parseSelectorGroup() (SelectorGroup, error) {
+	current, err := p.parseSelector()
 	if err != nil {
-		return
+		return nil, err
 	}
+	result := SelectorGroup{current}
 
 	for p.i < len(p.s) {
 		if p.s[p.i] != ',' {
-			return result, nil
+			break
 		}
 		p.i++
 		c, err := p.parseSelector()
 		if err != nil {
 			return nil, err
 		}
-		result = unionSelector(result, c)
+		result = append(result, c)
 	}
-
-	return
+	return result, nil
 }
diff --git a/vendor/github.com/andybalholm/cascadia/selector.go b/vendor/github.com/andybalholm/cascadia/selector.go
index 9fb05cc..e2a6dc4 100644
--- a/vendor/github.com/andybalholm/cascadia/selector.go
+++ b/vendor/github.com/andybalholm/cascadia/selector.go
@@ -9,36 +9,60 @@ import (
 	"golang.org/x/net/html"
 )
 
-// the Selector type, and functions for creating them
+// Matcher is the interface for basic selector functionality.
+// Match returns whether a selector matches n.
+type Matcher interface {
+	Match(n *html.Node) bool
+}
 
-// A Selector is a function which tells whether a node matches or not.
-type Selector func(*html.Node) bool
+// Sel is the interface for all the functionality provided by selectors.
+type Sel interface {
+	Matcher
+	Specificity() Specificity
 
-// hasChildMatch returns whether n has any child that matches a.
-func hasChildMatch(n *html.Node, a Selector) bool {
-	for c := n.FirstChild; c != nil; c = c.NextSibling {
-		if a(c) {
-			return true
-		}
+	// Returns a CSS input compiling to this selector.
+	String() string
+
+	// Returns a pseudo-element, or an empty string.
+	PseudoElement() string
+}
+
+// Parse parses a selector. Use `ParseWithPseudoElement`
+// if you need support for pseudo-elements.
+func Parse(sel string) (Sel, error) {
+	p := &parser{s: sel}
+	compiled, err := p.parseSelector()
+	if err != nil {
+		return nil, err
 	}
-	return false
+
+	if p.i < len(sel) {
+		return nil, fmt.Errorf("parsing %q: %d bytes left over", sel, len(sel)-p.i)
+	}
+
+	return compiled, nil
 }
 
-// hasDescendantMatch performs a depth-first search of n's descendants,
-// testing whether any of them match a. It returns true as soon as a match is
-// found, or false if no match is found.
-func hasDescendantMatch(n *html.Node, a Selector) bool {
-	for c := n.FirstChild; c != nil; c = c.NextSibling {
-		if a(c) || (c.Type == html.ElementNode && hasDescendantMatch(c, a)) {
-			return true
-		}
+// ParseWithPseudoElement parses a single selector,
+// with support for pseudo-element.
+func ParseWithPseudoElement(sel string) (Sel, error) {
+	p := &parser{s: sel, acceptPseudoElements: true}
+	compiled, err := p.parseSelector()
+	if err != nil {
+		return nil, err
 	}
-	return false
+
+	if p.i < len(sel) {
+		return nil, fmt.Errorf("parsing %q: %d bytes left over", sel, len(sel)-p.i)
+	}
+
+	return compiled, nil
 }
 
-// Compile parses a selector and returns, if successful, a Selector object
-// that can be used to match against html.Node objects.
-func Compile(sel string) (Selector, error) {
+// ParseGroup parses a selector, or a group of selectors separated by commas.
+// Use `ParseGroupWithPseudoElements`
+// if you need support for pseudo-elements.
+func ParseGroup(sel string) (SelectorGroup, error) {
 	p := &parser{s: sel}
 	compiled, err := p.parseSelectorGroup()
 	if err != nil {
@@ -52,6 +76,39 @@ func Compile(sel string) (Selector, error) {
 	return compiled, nil
 }
 
+// ParseGroupWithPseudoElements parses a selector, or a group of selectors separated by commas.
+// It supports pseudo-elements.
+func ParseGroupWithPseudoElements(sel string) (SelectorGroup, error) {
+	p := &parser{s: sel, acceptPseudoElements: true}
+	compiled, err := p.parseSelectorGroup()
+	if err != nil {
+		return nil, err
+	}
+
+	if p.i < len(sel) {
+		return nil, fmt.Errorf("parsing %q: %d bytes left over", sel, len(sel)-p.i)
+	}
+
+	return compiled, nil
+}
+
+// A Selector is a function which tells whether a node matches or not.
+//
+// This type is maintained for compatibility; I recommend using the newer and
+// more idiomatic interfaces Sel and Matcher.
+type Selector func(*html.Node) bool
+
+// Compile parses a selector and returns, if successful, a Selector object
+// that can be used to match against html.Node objects.
+func Compile(sel string) (Selector, error) {
+	compiled, err := ParseGroup(sel)
+	if err != nil {
+		return nil, err
+	}
+
+	return Selector(compiled.Match), nil
+}
+
 // MustCompile is like Compile, but panics instead of returning an error.
 func MustCompile(sel string) Selector {
 	compiled, err := Compile(sel)
@@ -79,6 +136,23 @@ func (s Selector) matchAllInto(n *html.Node, storage []*html.Node) []*html.Node
 	return storage
 }
 
+func queryInto(n *html.Node, m Matcher, storage []*html.Node) []*html.Node {
+	for child := n.FirstChild; child != nil; child = child.NextSibling {
+		if m.Match(child) {
+			storage = append(storage, child)
+		}
+		storage = queryInto(child, m, storage)
+	}
+
+	return storage
+}
+
+// QueryAll returns a slice of all the nodes that match m, from the descendants
+// of n.
+func QueryAll(n *html.Node, m Matcher) []*html.Node {
+	return queryInto(n, m, nil)
+}
+
 // Match returns true if the node matches the selector.
 func (s Selector) Match(n *html.Node) bool {
 	return s(n)
@@ -99,6 +173,21 @@ func (s Selector) MatchFirst(n *html.Node) *html.Node {
 	return nil
 }
 
+// Query returns the first node that matches m, from the descendants of n.
+// If none matches, it returns nil.
+func Query(n *html.Node, m Matcher) *html.Node {
+	for c := n.FirstChild; c != nil; c = c.NextSibling {
+		if m.Match(c) {
+			return c
+		}
+		if matched := Query(c, m); matched != nil {
+			return matched
+		}
+	}
+
+	return nil
+}
+
 // Filter returns the nodes in nodes that match the selector.
 func (s Selector) Filter(nodes []*html.Node) (result []*html.Node) {
 	for _, n := range nodes {
@@ -109,106 +198,148 @@ func (s Selector) Filter(nodes []*html.Node) (result []*html.Node) {
 	return result
 }
 
-// typeSelector returns a Selector that matches elements with a given tag name.
-func typeSelector(tag string) Selector {
-	tag = toLowerASCII(tag)
-	return func(n *html.Node) bool {
-		return n.Type == html.ElementNode && n.Data == tag
+// Filter returns the nodes that match m.
+func Filter(nodes []*html.Node, m Matcher) (result []*html.Node) {
+	for _, n := range nodes {
+		if m.Match(n) {
+			result = append(result, n)
+		}
 	}
+	return result
 }
 
-// toLowerASCII returns s with all ASCII capital letters lowercased.
-func toLowerASCII(s string) string {
-	var b []byte
-	for i := 0; i < len(s); i++ {
-		if c := s[i]; 'A' <= c && c <= 'Z' {
-			if b == nil {
-				b = make([]byte, len(s))
-				copy(b, s)
-			}
-			b[i] = s[i] + ('a' - 'A')
-		}
-	}
+type tagSelector struct {
+	tag string
+}
 
-	if b == nil {
-		return s
-	}
+// Matches elements with a given tag name.
+func (t tagSelector) Match(n *html.Node) bool {
+	return n.Type == html.ElementNode && n.Data == t.tag
+}
 
-	return string(b)
+func (c tagSelector) Specificity() Specificity {
+	return Specificity{0, 0, 1}
 }
 
-// attributeSelector returns a Selector that matches elements
-// where the attribute named key satisifes the function f.
-func attributeSelector(key string, f func(string) bool) Selector {
-	key = toLowerASCII(key)
-	return func(n *html.Node) bool {
-		if n.Type != html.ElementNode {
-			return false
-		}
-		for _, a := range n.Attr {
-			if a.Key == key && f(a.Val) {
-				return true
-			}
-		}
-		return false
-	}
+func (c tagSelector) PseudoElement() string {
+	return ""
 }
 
-// attributeExistsSelector returns a Selector that matches elements that have
-// an attribute named key.
-func attributeExistsSelector(key string) Selector {
-	return attributeSelector(key, func(string) bool { return true })
+type classSelector struct {
+	class string
 }
 
-// attributeEqualsSelector returns a Selector that matches elements where
-// the attribute named key has the value val.
-func attributeEqualsSelector(key, val string) Selector {
-	return attributeSelector(key,
-		func(s string) bool {
-			return s == val
-		})
+// Matches elements by class attribute.
+func (t classSelector) Match(n *html.Node) bool {
+	return matchAttribute(n, "class", func(s string) bool {
+		return matchInclude(t.class, s)
+	})
+}
+
+func (c classSelector) Specificity() Specificity {
+	return Specificity{0, 1, 0}
+}
+
+func (c classSelector) PseudoElement() string {
+	return ""
+}
+
+type idSelector struct {
+	id string
+}
+
+// Matches elements by id attribute.
+func (t idSelector) Match(n *html.Node) bool {
+	return matchAttribute(n, "id", func(s string) bool {
+		return s == t.id
+	})
+}
+
+func (c idSelector) Specificity() Specificity {
+	return Specificity{1, 0, 0}
+}
+
+func (c idSelector) PseudoElement() string {
+	return ""
+}
+
+type attrSelector struct {
+	key, val, operation string
+	regexp              *regexp.Regexp
+}
+
+// Matches elements by attribute value.
+func (t attrSelector) Match(n *html.Node) bool {
+	switch t.operation {
+	case "":
+		return matchAttribute(n, t.key, func(string) bool { return true })
+	case "=":
+		return matchAttribute(n, t.key, func(s string) bool { return s == t.val })
+	case "!=":
+		return attributeNotEqualMatch(t.key, t.val, n)
+	case "~=":
+		// matches elements where the attribute named key is a whitespace-separated list that includes val.
+		return matchAttribute(n, t.key, func(s string) bool { return matchInclude(t.val, s) })
+	case "|=":
+		return attributeDashMatch(t.key, t.val, n)
+	case "^=":
+		return attributePrefixMatch(t.key, t.val, n)
+	case "$=":
+		return attributeSuffixMatch(t.key, t.val, n)
+	case "*=":
+		return attributeSubstringMatch(t.key, t.val, n)
+	case "#=":
+		return attributeRegexMatch(t.key, t.regexp, n)
+	default:
+		panic(fmt.Sprintf("unsuported operation : %s", t.operation))
+	}
 }
 
-// attributeNotEqualSelector returns a Selector that matches elements where
+// matches elements where the attribute named key satisifes the function f.
+func matchAttribute(n *html.Node, key string, f func(string) bool) bool {
+	if n.Type != html.ElementNode {
+		return false
+	}
+	for _, a := range n.Attr {
+		if a.Key == key && f(a.Val) {
+			return true
+		}
+	}
+	return false
+}
+
+// attributeNotEqualMatch matches elements where
 // the attribute named key does not have the value val.
-func attributeNotEqualSelector(key, val string) Selector {
-	key = toLowerASCII(key)
-	return func(n *html.Node) bool {
-		if n.Type != html.ElementNode {
+func attributeNotEqualMatch(key, val string, n *html.Node) bool {
+	if n.Type != html.ElementNode {
+		return false
+	}
+	for _, a := range n.Attr {
+		if a.Key == key && a.Val == val {
 			return false
 		}
-		for _, a := range n.Attr {
-			if a.Key == key && a.Val == val {
-				return false
-			}
-		}
-		return true
 	}
+	return true
 }
 
-// attributeIncludesSelector returns a Selector that matches elements where
-// the attribute named key is a whitespace-separated list that includes val.
-func attributeIncludesSelector(key, val string) Selector {
-	return attributeSelector(key,
-		func(s string) bool {
-			for s != "" {
-				i := strings.IndexAny(s, " \t\r\n\f")
-				if i == -1 {
-					return s == val
-				}
-				if s[:i] == val {
-					return true
-				}
-				s = s[i+1:]
-			}
-			return false
-		})
+// returns true if s is a whitespace-separated list that includes val.
+func matchInclude(val, s string) bool {
+	for s != "" {
+		i := strings.IndexAny(s, " \t\r\n\f")
+		if i == -1 {
+			return s == val
+		}
+		if s[:i] == val {
+			return true
+		}
+		s = s[i+1:]
+	}
+	return false
 }
 
-// attributeDashmatchSelector returns a Selector that matches elements where
-// the attribute named key equals val or starts with val plus a hyphen.
-func attributeDashmatchSelector(key, val string) Selector {
-	return attributeSelector(key,
+//  matches elements where the attribute named key equals val or starts with val plus a hyphen.
+func attributeDashMatch(key, val string, n *html.Node) bool {
+	return matchAttribute(n, key,
 		func(s string) bool {
 			if s == val {
 				return true
@@ -223,10 +354,10 @@ func attributeDashmatchSelector(key, val string) Selector {
 		})
 }
 
-// attributePrefixSelector returns a Selector that matches elements where
+// attributePrefixMatch returns a Selector that matches elements where
 // the attribute named key starts with val.
-func attributePrefixSelector(key, val string) Selector {
-	return attributeSelector(key,
+func attributePrefixMatch(key, val string, n *html.Node) bool {
+	return matchAttribute(n, key,
 		func(s string) bool {
 			if strings.TrimSpace(s) == "" {
 				return false
@@ -235,10 +366,10 @@ func attributePrefixSelector(key, val string) Selector {
 		})
 }
 
-// attributeSuffixSelector returns a Selector that matches elements where
+// attributeSuffixMatch matches elements where
 // the attribute named key ends with val.
-func attributeSuffixSelector(key, val string) Selector {
-	return attributeSelector(key,
+func attributeSuffixMatch(key, val string, n *html.Node) bool {
+	return matchAttribute(n, key,
 		func(s string) bool {
 			if strings.TrimSpace(s) == "" {
 				return false
@@ -247,10 +378,10 @@ func attributeSuffixSelector(key, val string) Selector {
 		})
 }
 
-// attributeSubstringSelector returns a Selector that matches nodes where
+// attributeSubstringMatch matches nodes where
 // the attribute named key contains val.
-func attributeSubstringSelector(key, val string) Selector {
-	return attributeSelector(key,
+func attributeSubstringMatch(key, val string, n *html.Node) bool {
+	return matchAttribute(n, key,
 		func(s string) bool {
 			if strings.TrimSpace(s) == "" {
 				return false
@@ -259,39 +390,130 @@ func attributeSubstringSelector(key, val string) Selector {
 		})
 }
 
-// attributeRegexSelector returns a Selector that matches nodes where
+// attributeRegexMatch  matches nodes where
 // the attribute named key matches the regular expression rx
-func attributeRegexSelector(key string, rx *regexp.Regexp) Selector {
-	return attributeSelector(key,
+func attributeRegexMatch(key string, rx *regexp.Regexp, n *html.Node) bool {
+	return matchAttribute(n, key,
 		func(s string) bool {
 			return rx.MatchString(s)
 		})
 }
 
-// intersectionSelector returns a selector that matches nodes that match
-// both a and b.
-func intersectionSelector(a, b Selector) Selector {
-	return func(n *html.Node) bool {
-		return a(n) && b(n)
+func (c attrSelector) Specificity() Specificity {
+	return Specificity{0, 1, 0}
+}
+
+func (c attrSelector) PseudoElement() string {
+	return ""
+}
+
+// ---------------- Pseudo class selectors ----------------
+// we use severals concrete types of pseudo-class selectors
+
+type relativePseudoClassSelector struct {
+	name  string // one of "not", "has", "haschild"
+	match SelectorGroup
+}
+
+func (s relativePseudoClassSelector) Match(n *html.Node) bool {
+	if n.Type != html.ElementNode {
+		return false
+	}
+	switch s.name {
+	case "not":
+		// matches elements that do not match a.
+		return !s.match.Match(n)
+	case "has":
+		//  matches elements with any descendant that matches a.
+		return hasDescendantMatch(n, s.match)
+	case "haschild":
+		// matches elements with a child that matches a.
+		return hasChildMatch(n, s.match)
+	default:
+		panic(fmt.Sprintf("unsupported relative pseudo class selector : %s", s.name))
 	}
 }
 
-// unionSelector returns a selector that matches elements that match
-// either a or b.
-func unionSelector(a, b Selector) Selector {
-	return func(n *html.Node) bool {
-		return a(n) || b(n)
+// hasChildMatch returns whether n has any child that matches a.
+func hasChildMatch(n *html.Node, a Matcher) bool {
+	for c := n.FirstChild; c != nil; c = c.NextSibling {
+		if a.Match(c) {
+			return true
+		}
 	}
+	return false
 }
 
-// negatedSelector returns a selector that matches elements that do not match a.
-func negatedSelector(a Selector) Selector {
-	return func(n *html.Node) bool {
-		if n.Type != html.ElementNode {
-			return false
+// hasDescendantMatch performs a depth-first search of n's descendants,
+// testing whether any of them match a. It returns true as soon as a match is
+// found, or false if no match is found.
+func hasDescendantMatch(n *html.Node, a Matcher) bool {
+	for c := n.FirstChild; c != nil; c = c.NextSibling {
+		if a.Match(c) || (c.Type == html.ElementNode && hasDescendantMatch(c, a)) {
+			return true
 		}
-		return !a(n)
 	}
+	return false
+}
+
+// Specificity returns the specificity of the most specific selectors
+// in the pseudo-class arguments.
+// See https://www.w3.org/TR/selectors/#specificity-rules
+func (s relativePseudoClassSelector) Specificity() Specificity {
+	var max Specificity
+	for _, sel := range s.match {
+		newSpe := sel.Specificity()
+		if max.Less(newSpe) {
+			max = newSpe
+		}
+	}
+	return max
+}
+
+func (c relativePseudoClassSelector) PseudoElement() string {
+	return ""
+}
+
+type containsPseudoClassSelector struct {
+	own   bool
+	value string
+}
+
+func (s containsPseudoClassSelector) Match(n *html.Node) bool {
+	var text string
+	if s.own {
+		// matches nodes that directly contain the given text
+		text = strings.ToLower(nodeOwnText(n))
+	} else {
+		// matches nodes that contain the given text.
+		text = strings.ToLower(nodeText(n))
+	}
+	return strings.Contains(text, s.value)
+}
+
+func (s containsPseudoClassSelector) Specificity() Specificity {
+	return Specificity{0, 1, 0}
+}
+
+func (c containsPseudoClassSelector) PseudoElement() string {
+	return ""
+}
+
+type regexpPseudoClassSelector struct {
+	own    bool
+	regexp *regexp.Regexp
+}
+
+func (s regexpPseudoClassSelector) Match(n *html.Node) bool {
+	var text string
+	if s.own {
+		// matches nodes whose text directly matches the specified regular expression
+		text = nodeOwnText(n)
+	} else {
+		// matches nodes whose text matches the specified regular expression
+		text = nodeText(n)
+	}
+	return s.regexp.MatchString(text)
 }
 
 // writeNodeText writes the text contained in n and its descendants to b.
@@ -325,221 +547,214 @@ func nodeOwnText(n *html.Node) string {
 	return b.String()
 }
 
-// textSubstrSelector returns a selector that matches nodes that
-// contain the given text.
-func textSubstrSelector(val string) Selector {
-	return func(n *html.Node) bool {
-		text := strings.ToLower(nodeText(n))
-		return strings.Contains(text, val)
-	}
-}
-
-// ownTextSubstrSelector returns a selector that matches nodes that
-// directly contain the given text
-func ownTextSubstrSelector(val string) Selector {
-	return func(n *html.Node) bool {
-		text := strings.ToLower(nodeOwnText(n))
-		return strings.Contains(text, val)
-	}
-}
-
-// textRegexSelector returns a selector that matches nodes whose text matches
-// the specified regular expression
-func textRegexSelector(rx *regexp.Regexp) Selector {
-	return func(n *html.Node) bool {
-		return rx.MatchString(nodeText(n))
-	}
+func (s regexpPseudoClassSelector) Specificity() Specificity {
+	return Specificity{0, 1, 0}
 }
 
-// ownTextRegexSelector returns a selector that matches nodes whose text
-// directly matches the specified regular expression
-func ownTextRegexSelector(rx *regexp.Regexp) Selector {
-	return func(n *html.Node) bool {
-		return rx.MatchString(nodeOwnText(n))
-	}
+func (c regexpPseudoClassSelector) PseudoElement() string {
+	return ""
 }
 
-// hasChildSelector returns a selector that matches elements
-// with a child that matches a.
-func hasChildSelector(a Selector) Selector {
-	return func(n *html.Node) bool {
-		if n.Type != html.ElementNode {
-			return false
-		}
-		return hasChildMatch(n, a)
-	}
+type nthPseudoClassSelector struct {
+	a, b         int
+	last, ofType bool
 }
 
-// hasDescendantSelector returns a selector that matches elements
-// with any descendant that matches a.
-func hasDescendantSelector(a Selector) Selector {
-	return func(n *html.Node) bool {
-		if n.Type != html.ElementNode {
-			return false
+func (s nthPseudoClassSelector) Match(n *html.Node) bool {
+	if s.a == 0 {
+		if s.last {
+			return simpleNthLastChildMatch(s.b, s.ofType, n)
+		} else {
+			return simpleNthChildMatch(s.b, s.ofType, n)
 		}
-		return hasDescendantMatch(n, a)
 	}
+	return nthChildMatch(s.a, s.b, s.last, s.ofType, n)
 }
 
-// nthChildSelector returns a selector that implements :nth-child(an+b).
+// nthChildMatch implements :nth-child(an+b).
 // If last is true, implements :nth-last-child instead.
 // If ofType is true, implements :nth-of-type instead.
-func nthChildSelector(a, b int, last, ofType bool) Selector {
-	return func(n *html.Node) bool {
-		if n.Type != html.ElementNode {
-			return false
-		}
+func nthChildMatch(a, b int, last, ofType bool, n *html.Node) bool {
+	if n.Type != html.ElementNode {
+		return false
+	}
 
-		parent := n.Parent
-		if parent == nil {
-			return false
-		}
+	parent := n.Parent
+	if parent == nil {
+		return false
+	}
 
-		if parent.Type == html.DocumentNode {
-			return false
-		}
+	if parent.Type == html.DocumentNode {
+		return false
+	}
 
-		i := -1
-		count := 0
-		for c := parent.FirstChild; c != nil; c = c.NextSibling {
-			if (c.Type != html.ElementNode) || (ofType && c.Data != n.Data) {
-				continue
-			}
-			count++
-			if c == n {
-				i = count
-				if !last {
-					break
-				}
-			}
+	i := -1
+	count := 0
+	for c := parent.FirstChild; c != nil; c = c.NextSibling {
+		if (c.Type != html.ElementNode) || (ofType && c.Data != n.Data) {
+			continue
 		}
-
-		if i == -1 {
-			// This shouldn't happen, since n should always be one of its parent's children.
-			return false
+		count++
+		if c == n {
+			i = count
+			if !last {
+				break
+			}
 		}
+	}
 
-		if last {
-			i = count - i + 1
-		}
+	if i == -1 {
+		// This shouldn't happen, since n should always be one of its parent's children.
+		return false
+	}
 
-		i -= b
-		if a == 0 {
-			return i == 0
-		}
+	if last {
+		i = count - i + 1
+	}
 
-		return i%a == 0 && i/a >= 0
+	i -= b
+	if a == 0 {
+		return i == 0
 	}
+
+	return i%a == 0 && i/a >= 0
 }
 
-// simpleNthChildSelector returns a selector that implements :nth-child(b).
+// simpleNthChildMatch implements :nth-child(b).
 // If ofType is true, implements :nth-of-type instead.
-func simpleNthChildSelector(b int, ofType bool) Selector {
-	return func(n *html.Node) bool {
-		if n.Type != html.ElementNode {
-			return false
-		}
+func simpleNthChildMatch(b int, ofType bool, n *html.Node) bool {
+	if n.Type != html.ElementNode {
+		return false
+	}
 
-		parent := n.Parent
-		if parent == nil {
-			return false
-		}
+	parent := n.Parent
+	if parent == nil {
+		return false
+	}
+
+	if parent.Type == html.DocumentNode {
+		return false
+	}
 
-		if parent.Type == html.DocumentNode {
+	count := 0
+	for c := parent.FirstChild; c != nil; c = c.NextSibling {
+		if c.Type != html.ElementNode || (ofType && c.Data != n.Data) {
+			continue
+		}
+		count++
+		if c == n {
+			return count == b
+		}
+		if count >= b {
 			return false
 		}
+	}
+	return false
+}
 
-		count := 0
-		for c := parent.FirstChild; c != nil; c = c.NextSibling {
-			if c.Type != html.ElementNode || (ofType && c.Data != n.Data) {
-				continue
-			}
-			count++
-			if c == n {
-				return count == b
-			}
-			if count >= b {
-				return false
-			}
-		}
+// simpleNthLastChildMatch implements :nth-last-child(b).
+// If ofType is true, implements :nth-last-of-type instead.
+func simpleNthLastChildMatch(b int, ofType bool, n *html.Node) bool {
+	if n.Type != html.ElementNode {
 		return false
 	}
-}
 
-// simpleNthLastChildSelector returns a selector that implements
-// :nth-last-child(b). If ofType is true, implements :nth-last-of-type
-// instead.
-func simpleNthLastChildSelector(b int, ofType bool) Selector {
-	return func(n *html.Node) bool {
-		if n.Type != html.ElementNode {
-			return false
-		}
+	parent := n.Parent
+	if parent == nil {
+		return false
+	}
 
-		parent := n.Parent
-		if parent == nil {
-			return false
-		}
+	if parent.Type == html.DocumentNode {
+		return false
+	}
 
-		if parent.Type == html.DocumentNode {
+	count := 0
+	for c := parent.LastChild; c != nil; c = c.PrevSibling {
+		if c.Type != html.ElementNode || (ofType && c.Data != n.Data) {
+			continue
+		}
+		count++
+		if c == n {
+			return count == b
+		}
+		if count >= b {
 			return false
 		}
+	}
+	return false
+}
 
-		count := 0
-		for c := parent.LastChild; c != nil; c = c.PrevSibling {
-			if c.Type != html.ElementNode || (ofType && c.Data != n.Data) {
-				continue
-			}
-			count++
-			if c == n {
-				return count == b
-			}
-			if count >= b {
-				return false
-			}
-		}
+// Specificity for nth-child pseudo-class.
+// Does not support a list of selectors
+func (s nthPseudoClassSelector) Specificity() Specificity {
+	return Specificity{0, 1, 0}
+}
+
+func (c nthPseudoClassSelector) PseudoElement() string {
+	return ""
+}
+
+type onlyChildPseudoClassSelector struct {
+	ofType bool
+}
+
+// Match implements :only-child.
+// If `ofType` is true, it implements :only-of-type instead.
+func (s onlyChildPseudoClassSelector) Match(n *html.Node) bool {
+	if n.Type != html.ElementNode {
 		return false
 	}
-}
 
-// onlyChildSelector returns a selector that implements :only-child.
-// If ofType is true, it implements :only-of-type instead.
-func onlyChildSelector(ofType bool) Selector {
-	return func(n *html.Node) bool {
-		if n.Type != html.ElementNode {
-			return false
-		}
+	parent := n.Parent
+	if parent == nil {
+		return false
+	}
 
-		parent := n.Parent
-		if parent == nil {
-			return false
-		}
+	if parent.Type == html.DocumentNode {
+		return false
+	}
 
-		if parent.Type == html.DocumentNode {
+	count := 0
+	for c := parent.FirstChild; c != nil; c = c.NextSibling {
+		if (c.Type != html.ElementNode) || (s.ofType && c.Data != n.Data) {
+			continue
+		}
+		count++
+		if count > 1 {
 			return false
 		}
+	}
 
-		count := 0
-		for c := parent.FirstChild; c != nil; c = c.NextSibling {
-			if (c.Type != html.ElementNode) || (ofType && c.Data != n.Data) {
-				continue
-			}
-			count++
-			if count > 1 {
-				return false
-			}
-		}
+	return count == 1
+}
 
-		return count == 1
-	}
+func (s onlyChildPseudoClassSelector) Specificity() Specificity {
+	return Specificity{0, 1, 0}
 }
 
-// inputSelector is a Selector that matches input, select, textarea and button elements.
-func inputSelector(n *html.Node) bool {
+func (c onlyChildPseudoClassSelector) PseudoElement() string {
+	return ""
+}
+
+type inputPseudoClassSelector struct{}
+
+// Matches input, select, textarea and button elements.
+func (s inputPseudoClassSelector) Match(n *html.Node) bool {
 	return n.Type == html.ElementNode && (n.Data == "input" || n.Data == "select" || n.Data == "textarea" || n.Data == "button")
 }
 
-// emptyElementSelector is a Selector that matches empty elements.
-func emptyElementSelector(n *html.Node) bool {
+func (s inputPseudoClassSelector) Specificity() Specificity {
+	return Specificity{0, 1, 0}
+}
+
+func (c inputPseudoClassSelector) PseudoElement() string {
+	return ""
+}
+
+type emptyElementPseudoClassSelector struct{}
+
+// Matches empty elements.
+func (s emptyElementPseudoClassSelector) Match(n *html.Node) bool {
 	if n.Type != html.ElementNode {
 		return false
 	}
@@ -554,69 +769,170 @@ func emptyElementSelector(n *html.Node) bool {
 	return true
 }
 
-// descendantSelector returns a Selector that matches an element if
-// it matches d and has an ancestor that matches a.
-func descendantSelector(a, d Selector) Selector {
-	return func(n *html.Node) bool {
-		if !d(n) {
+func (s emptyElementPseudoClassSelector) Specificity() Specificity {
+	return Specificity{0, 1, 0}
+}
+
+func (c emptyElementPseudoClassSelector) PseudoElement() string {
+	return ""
+}
+
+type rootPseudoClassSelector struct{}
+
+// Match implements :root
+func (s rootPseudoClassSelector) Match(n *html.Node) bool {
+	if n.Type != html.ElementNode {
+		return false
+	}
+	if n.Parent == nil {
+		return false
+	}
+	return n.Parent.Type == html.DocumentNode
+}
+
+func (s rootPseudoClassSelector) Specificity() Specificity {
+	return Specificity{0, 1, 0}
+}
+
+func (c rootPseudoClassSelector) PseudoElement() string {
+	return ""
+}
+
+type compoundSelector struct {
+	selectors     []Sel
+	pseudoElement string
+}
+
+// Matches elements if each sub-selectors matches.
+func (t compoundSelector) Match(n *html.Node) bool {
+	if len(t.selectors) == 0 {
+		return n.Type == html.ElementNode
+	}
+
+	for _, sel := range t.selectors {
+		if !sel.Match(n) {
 			return false
 		}
+	}
+	return true
+}
 
-		for p := n.Parent; p != nil; p = p.Parent {
-			if a(p) {
-				return true
-			}
-		}
+func (s compoundSelector) Specificity() Specificity {
+	var out Specificity
+	for _, sel := range s.selectors {
+		out = out.Add(sel.Specificity())
+	}
+	if s.pseudoElement != "" {
+		// https://drafts.csswg.org/selectors-3/#specificity
+		out = out.Add(Specificity{0, 0, 1})
+	}
+	return out
+}
 
-		return false
+func (c compoundSelector) PseudoElement() string {
+	return c.pseudoElement
+}
+
+type combinedSelector struct {
+	first      Sel
+	combinator byte
+	second     Sel
+}
+
+func (t combinedSelector) Match(n *html.Node) bool {
+	if t.first == nil {
+		return false // maybe we should panic
+	}
+	switch t.combinator {
+	case 0:
+		return t.first.Match(n)
+	case ' ':
+		return descendantMatch(t.first, t.second, n)
+	case '>':
+		return childMatch(t.first, t.second, n)
+	case '+':
+		return siblingMatch(t.first, t.second, true, n)
+	case '~':
+		return siblingMatch(t.first, t.second, false, n)
+	default:
+		panic("unknown combinator")
 	}
 }
 
-// childSelector returns a Selector that matches an element if
-// it matches d and its parent matches a.
-func childSelector(a, d Selector) Selector {
-	return func(n *html.Node) bool {
-		return d(n) && n.Parent != nil && a(n.Parent)
+// matches an element if it matches d and has an ancestor that matches a.
+func descendantMatch(a, d Matcher, n *html.Node) bool {
+	if !d.Match(n) {
+		return false
 	}
+
+	for p := n.Parent; p != nil; p = p.Parent {
+		if a.Match(p) {
+			return true
+		}
+	}
+
+	return false
 }
 
-// siblingSelector returns a Selector that matches an element
-// if it matches s2 and in is preceded by an element that matches s1.
+// matches an element if it matches d and its parent matches a.
+func childMatch(a, d Matcher, n *html.Node) bool {
+	return d.Match(n) && n.Parent != nil && a.Match(n.Parent)
+}
+
+// matches an element if it matches s2 and is preceded by an element that matches s1.
 // If adjacent is true, the sibling must be immediately before the element.
-func siblingSelector(s1, s2 Selector, adjacent bool) Selector {
-	return func(n *html.Node) bool {
-		if !s2(n) {
-			return false
-		}
+func siblingMatch(s1, s2 Matcher, adjacent bool, n *html.Node) bool {
+	if !s2.Match(n) {
+		return false
+	}
 
-		if adjacent {
-			for n = n.PrevSibling; n != nil; n = n.PrevSibling {
-				if n.Type == html.TextNode || n.Type == html.CommentNode {
-					continue
-				}
-				return s1(n)
+	if adjacent {
+		for n = n.PrevSibling; n != nil; n = n.PrevSibling {
+			if n.Type == html.TextNode || n.Type == html.CommentNode {
+				continue
 			}
-			return false
+			return s1.Match(n)
 		}
+		return false
+	}
 
-		// Walk backwards looking for element that matches s1
-		for c := n.PrevSibling; c != nil; c = c.PrevSibling {
-			if s1(c) {
-				return true
-			}
+	// Walk backwards looking for element that matches s1
+	for c := n.PrevSibling; c != nil; c = c.PrevSibling {
+		if s1.Match(c) {
+			return true
 		}
+	}
 
-		return false
+	return false
+}
+
+func (s combinedSelector) Specificity() Specificity {
+	spec := s.first.Specificity()
+	if s.second != nil {
+		spec = spec.Add(s.second.Specificity())
 	}
+	return spec
 }
 
-// rootSelector implements :root
-func rootSelector(n *html.Node) bool {
-	if n.Type != html.ElementNode {
-		return false
+// on combinedSelector, a pseudo-element only makes sens on the last
+// selector, although others increase specificity.
+func (c combinedSelector) PseudoElement() string {
+	if c.second == nil {
+		return ""
 	}
-	if n.Parent == nil {
-		return false
+	return c.second.PseudoElement()
+}
+
+// A SelectorGroup is a list of selectors, which matches if any of the
+// individual selectors matches.
+type SelectorGroup []Sel
+
+// Match returns true if the node matches one of the single selectors.
+func (s SelectorGroup) Match(n *html.Node) bool {
+	for _, sel := range s {
+		if sel.Match(n) {
+			return true
+		}
 	}
-	return n.Parent.Type == html.DocumentNode
+	return false
 }
diff --git a/vendor/github.com/andybalholm/cascadia/serialize.go b/vendor/github.com/andybalholm/cascadia/serialize.go
new file mode 100644
index 0000000..f15b079
--- /dev/null
+++ b/vendor/github.com/andybalholm/cascadia/serialize.go
@@ -0,0 +1,120 @@
+package cascadia
+
+import (
+	"fmt"
+	"strings"
+)
+
+// implements the reverse operation Sel -> string
+
+func (c tagSelector) String() string {
+	return c.tag
+}
+
+func (c idSelector) String() string {
+	return "#" + c.id
+}
+
+func (c classSelector) String() string {
+	return "." + c.class
+}
+
+func (c attrSelector) String() string {
+	val := c.val
+	if c.operation == "#=" {
+		val = c.regexp.String()
+	} else if c.operation != "" {
+		val = fmt.Sprintf(`"%s"`, val)
+	}
+	return fmt.Sprintf(`[%s%s%s]`, c.key, c.operation, val)
+}
+
+func (c relativePseudoClassSelector) String() string {
+	return fmt.Sprintf(":%s(%s)", c.name, c.match.String())
+}
+func (c containsPseudoClassSelector) String() string {
+	s := "contains"
+	if c.own {
+		s += "Own"
+	}
+	return fmt.Sprintf(`:%s("%s")`, s, c.value)
+}
+func (c regexpPseudoClassSelector) String() string {
+	s := "matches"
+	if c.own {
+		s += "Own"
+	}
+	return fmt.Sprintf(":%s(%s)", s, c.regexp.String())
+}
+func (c nthPseudoClassSelector) String() string {
+	if c.a == 0 && c.b == 1 { // special cases
+		s := ":first-"
+		if c.last {
+			s = ":last-"
+		}
+		if c.ofType {
+			s += "of-type"
+		} else {
+			s += "child"
+		}
+		return s
+	}
+	var name string
+	switch [2]bool{c.last, c.ofType} {
+	case [2]bool{true, true}:
+		name = "nth-last-of-type"
+	case [2]bool{true, false}:
+		name = "nth-last-child"
+	case [2]bool{false, true}:
+		name = "nth-of-type"
+	case [2]bool{false, false}:
+		name = "nth-child"
+	}
+	return fmt.Sprintf(":%s(%dn+%d)", name, c.a, c.b)
+}
+func (c onlyChildPseudoClassSelector) String() string {
+	if c.ofType {
+		return ":only-of-type"
+	}
+	return ":only-child"
+}
+func (c inputPseudoClassSelector) String() string {
+	return ":input"
+}
+func (c emptyElementPseudoClassSelector) String() string {
+	return ":empty"
+}
+func (c rootPseudoClassSelector) String() string {
+	return ":root"
+}
+
+func (c compoundSelector) String() string {
+	if len(c.selectors) == 0 && c.pseudoElement == "" {
+		return "*"
+	}
+	chunks := make([]string, len(c.selectors))
+	for i, sel := range c.selectors {
+		chunks[i] = sel.String()
+	}
+	s := strings.Join(chunks, "")
+	if c.pseudoElement != "" {
+		s += "::" + c.pseudoElement
+	}
+	return s
+}
+
+func (c combinedSelector) String() string {
+	start := c.first.String()
+	if c.second != nil {
+		start += fmt.Sprintf(" %s %s", string(c.combinator), c.second.String())
+	}
+	return start
+}
+
+func (c SelectorGroup) String() string {
+	ck := make([]string, len(c))
+	for i, s := range c {
+		ck[i] = s.String()
+	}
+	return strings.Join(ck, ", ")
+}
diff --git a/vendor/github.com/andybalholm/cascadia/specificity.go b/vendor/github.com/andybalholm/cascadia/specificity.go
new file mode 100644
index 0000000..8db864f
--- /dev/null
+++ b/vendor/github.com/andybalholm/cascadia/specificity.go
@@ -0,0 +1,26 @@
+package cascadia
+
+// Specificity is the CSS specificity as defined in
+// https://www.w3.org/TR/selectors/#specificity-rules
+// with the convention Specificity = [A,B,C].
+type Specificity [3]int
+
+// returns `true` if s < other (strictly), false otherwise
+func (s Specificity) Less(other Specificity) bool {
+	for i := range s {
+		if s[i] < other[i] {
+			return true
+		}
+		if s[i] > other[i] {
+			return false
+		}
+	}
+	return false
+}
+
+func (s Specificity) Add(other Specificity) Specificity {
+	for i, sp := range other {
+		s[i] += sp
+	}
+	return s
+}
diff --git a/vendor/github.com/google/go-cmp/cmp/export_unsafe.go b/vendor/github.com/google/go-cmp/cmp/export_unsafe.go
index 59d4ee9..5f6ed93 100644
--- a/vendor/github.com/google/go-cmp/cmp/export_unsafe.go
+++ b/vendor/github.com/google/go-cmp/cmp/export_unsafe.go
@@ -19,5 +19,7 @@ const supportAllowUnexported = true
 // The parent struct, v, must be addressable, while f must be a StructField
 // describing the field to retrieve.
 func retrieveUnexportedField(v reflect.Value, f reflect.StructField) reflect.Value {
-	return reflect.NewAt(f.Type, unsafe.Pointer(v.UnsafeAddr()+f.Offset)).Elem()
+	// See https://github.com/google/go-cmp/issues/167 for discussion of the
+	// following expression.
+	return reflect.NewAt(f.Type, unsafe.Pointer(uintptr(unsafe.Pointer(v.UnsafeAddr()))+f.Offset)).Elem()
 }
diff --git a/vendor/github.com/google/go-cmp/cmp/options.go b/vendor/github.com/google/go-cmp/cmp/options.go
index 7934481..a20390d 100644
--- a/vendor/github.com/google/go-cmp/cmp/options.go
+++ b/vendor/github.com/google/go-cmp/cmp/options.go
@@ -226,7 +226,19 @@ func (validator) apply(s *state, vx, vy reflect.Value) {
 	// Unable to Interface implies unexported field without visibility access.
 	if !vx.CanInterface() || !vy.CanInterface() {
 		const help = "consider using a custom Comparer; if you control the implementation of type, you can also consider AllowUnexported or cmpopts.IgnoreUnexported"
-		panic(fmt.Sprintf("cannot handle unexported field: %#v\n%s", s.curPath, help))
+		var name string
+		if t := s.curPath.Index(-2).Type(); t.Name() != "" {
+			// Named type with unexported fields.
+			name = fmt.Sprintf("%q.%v", t.PkgPath(), t.Name()) // e.g., "path/to/package".MyType
+		} else {
+			// Unnamed type with unexported fields. Derive PkgPath from field.
+			var pkgPath string
+			for i := 0; i < t.NumField() && pkgPath == ""; i++ {
+				pkgPath = t.Field(i).PkgPath
+			}
+			name = fmt.Sprintf("%q.(%v)", pkgPath, t.String()) // e.g., "path/to/package".(struct { a int })
+		}
+		panic(fmt.Sprintf("cannot handle unexported field at %#v:\n\t%v\n%s", s.curPath, name, help))
 	}
 
 	panic("not reachable")
diff --git a/vendor/github.com/google/uuid/CONTRIBUTING.md b/vendor/github.com/google/uuid/CONTRIBUTING.md
new file mode 100644
index 0000000..04fdf09
--- /dev/null
+++ b/vendor/github.com/google/uuid/CONTRIBUTING.md
@@ -0,0 +1,10 @@
+# How to contribute
+
+We definitely welcome patches and contribution to this project!
+
+### Legal requirements
+
+In order to protect both you and ourselves, you will need to sign the
+[Contributor License Agreement](https://cla.developers.google.com/clas).
+
+You may have already signed it for other Google projects.
diff --git a/vendor/github.com/google/uuid/CONTRIBUTORS b/vendor/github.com/google/uuid/CONTRIBUTORS
new file mode 100644
index 0000000..b4bb97f
--- /dev/null
+++ b/vendor/github.com/google/uuid/CONTRIBUTORS
@@ -0,0 +1,9 @@
+Paul Borman <borman@google.com>
+bmatsuo
+shawnps
+theory
+jboverfelt
+dsymonds
+cd1
+wallclockbuilder
+dansouza
diff --git a/vendor/github.com/google/uuid/LICENSE b/vendor/github.com/google/uuid/LICENSE
new file mode 100644
index 0000000..5dc6826
--- /dev/null
+++ b/vendor/github.com/google/uuid/LICENSE
@@ -0,0 +1,27 @@
+Copyright (c) 2009,2014 Google Inc. All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are
+met:
+
+   * Redistributions of source code must retain the above copyright
+notice, this list of conditions and the following disclaimer.
+   * Redistributions in binary form must reproduce the above
+copyright notice, this list of conditions and the following disclaimer
+in the documentation and/or other materials provided with the
+distribution.
+   * Neither the name of Google Inc. nor the names of its
+contributors may be used to endorse or promote products derived from
+this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
diff --git a/vendor/github.com/google/uuid/README.md b/vendor/github.com/google/uuid/README.md
new file mode 100644
index 0000000..9d92c11
--- /dev/null
+++ b/vendor/github.com/google/uuid/README.md
@@ -0,0 +1,19 @@
+# uuid ![build status](https://travis-ci.org/google/uuid.svg?branch=master)
+The uuid package generates and inspects UUIDs based on
+[RFC 4122](http://tools.ietf.org/html/rfc4122)
+and DCE 1.1: Authentication and Security Services. 
+
+This package is based on the github.com/pborman/uuid package (previously named
+code.google.com/p/go-uuid).  It differs from these earlier packages in that
+a UUID is a 16 byte array rather than a byte slice.  One loss due to this
+change is the ability to represent an invalid UUID (vs a NIL UUID).
+
+###### Install
+`go get github.com/google/uuid`
+
+###### Documentation 
+[![GoDoc](https://godoc.org/github.com/google/uuid?status.svg)](http://godoc.org/github.com/google/uuid)
+
+Full `go doc` style documentation for the package can be viewed online without
+installing this package by using the GoDoc site here: 
+http://godoc.org/github.com/google/uuid
diff --git a/vendor/github.com/google/uuid/dce.go b/vendor/github.com/google/uuid/dce.go
new file mode 100644
index 0000000..fa820b9
--- /dev/null
+++ b/vendor/github.com/google/uuid/dce.go
@@ -0,0 +1,80 @@
+// Copyright 2016 Google Inc.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package uuid
+
+import (
+	"encoding/binary"
+	"fmt"
+	"os"
+)
+
+// A Domain represents a Version 2 domain
+type Domain byte
+
+// Domain constants for DCE Security (Version 2) UUIDs.
+const (
+	Person = Domain(0)
+	Group  = Domain(1)
+	Org    = Domain(2)
+)
+
+// NewDCESecurity returns a DCE Security (Version 2) UUID.
+//
+// The domain should be one of Person, Group or Org.
+// On a POSIX system the id should be the users UID for the Person
+// domain and the users GID for the Group.  The meaning of id for
+// the domain Org or on non-POSIX systems is site defined.
+//
+// For a given domain/id pair the same token may be returned for up to
+// 7 minutes and 10 seconds.
+func NewDCESecurity(domain Domain, id uint32) (UUID, error) {
+	uuid, err := NewUUID()
+	if err == nil {
+		uuid[6] = (uuid[6] & 0x0f) | 0x20 // Version 2
+		uuid[9] = byte(domain)
+		binary.BigEndian.PutUint32(uuid[0:], id)
+	}
+	return uuid, err
+}
+
+// NewDCEPerson returns a DCE Security (Version 2) UUID in the person
+// domain with the id returned by os.Getuid.
+//
+//  NewDCESecurity(Person, uint32(os.Getuid()))
+func NewDCEPerson() (UUID, error) {
+	return NewDCESecurity(Person, uint32(os.Getuid()))
+}
+
+// NewDCEGroup returns a DCE Security (Version 2) UUID in the group
+// domain with the id returned by os.Getgid.
+//
+//  NewDCESecurity(Group, uint32(os.Getgid()))
+func NewDCEGroup() (UUID, error) {
+	return NewDCESecurity(Group, uint32(os.Getgid()))
+}
+
+// Domain returns the domain for a Version 2 UUID.  Domains are only defined
+// for Version 2 UUIDs.
+func (uuid UUID) Domain() Domain {
+	return Domain(uuid[9])
+}
+
+// ID returns the id for a Version 2 UUID. IDs are only defined for Version 2
+// UUIDs.
+func (uuid UUID) ID() uint32 {
+	return binary.BigEndian.Uint32(uuid[0:4])
+}
+
+func (d Domain) String() string {
+	switch d {
+	case Person:
+		return "Person"
+	case Group:
+		return "Group"
+	case Org:
+		return "Org"
+	}
+	return fmt.Sprintf("Domain%d", int(d))
+}
diff --git a/vendor/github.com/google/uuid/doc.go b/vendor/github.com/google/uuid/doc.go
new file mode 100644
index 0000000..5b8a4b9
--- /dev/null
+++ b/vendor/github.com/google/uuid/doc.go
@@ -0,0 +1,12 @@
+// Copyright 2016 Google Inc.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package uuid generates and inspects UUIDs.
+//
+// UUIDs are based on RFC 4122 and DCE 1.1: Authentication and Security
+// Services.
+//
+// A UUID is a 16 byte (128 bit) array.  UUIDs may be used as keys to
+// maps or compared directly.
+package uuid
diff --git a/vendor/github.com/google/uuid/go.mod b/vendor/github.com/google/uuid/go.mod
new file mode 100644
index 0000000..fc84cd7
--- /dev/null
+++ b/vendor/github.com/google/uuid/go.mod
@@ -0,0 +1 @@
+module github.com/google/uuid
diff --git a/vendor/github.com/google/uuid/hash.go b/vendor/github.com/google/uuid/hash.go
new file mode 100644
index 0000000..b174616
--- /dev/null
+++ b/vendor/github.com/google/uuid/hash.go
@@ -0,0 +1,53 @@
+// Copyright 2016 Google Inc.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package uuid
+
+import (
+	"crypto/md5"
+	"crypto/sha1"
+	"hash"
+)
+
+// Well known namespace IDs and UUIDs
+var (
+	NameSpaceDNS  = Must(Parse("6ba7b810-9dad-11d1-80b4-00c04fd430c8"))
+	NameSpaceURL  = Must(Parse("6ba7b811-9dad-11d1-80b4-00c04fd430c8"))
+	NameSpaceOID  = Must(Parse("6ba7b812-9dad-11d1-80b4-00c04fd430c8"))
+	NameSpaceX500 = Must(Parse("6ba7b814-9dad-11d1-80b4-00c04fd430c8"))
+	Nil           UUID // empty UUID, all zeros
+)
+
+// NewHash returns a new UUID derived from the hash of space concatenated with
+// data generated by h.  The hash should be at least 16 byte in length.  The
+// first 16 bytes of the hash are used to form the UUID.  The version of the
+// UUID will be the lower 4 bits of version.  NewHash is used to implement
+// NewMD5 and NewSHA1.
+func NewHash(h hash.Hash, space UUID, data []byte, version int) UUID {
+	h.Reset()
+	h.Write(space[:])
+	h.Write(data)
+	s := h.Sum(nil)
+	var uuid UUID
+	copy(uuid[:], s)
+	uuid[6] = (uuid[6] & 0x0f) | uint8((version&0xf)<<4)
+	uuid[8] = (uuid[8] & 0x3f) | 0x80 // RFC 4122 variant
+	return uuid
+}
+
+// NewMD5 returns a new MD5 (Version 3) UUID based on the
+// supplied name space and data.  It is the same as calling:
+//
+//  NewHash(md5.New(), space, data, 3)
+func NewMD5(space UUID, data []byte) UUID {
+	return NewHash(md5.New(), space, data, 3)
+}
+
+// NewSHA1 returns a new SHA1 (Version 5) UUID based on the
+// supplied name space and data.  It is the same as calling:
+//
+//  NewHash(sha1.New(), space, data, 5)
+func NewSHA1(space UUID, data []byte) UUID {
+	return NewHash(sha1.New(), space, data, 5)
+}
diff --git a/vendor/github.com/google/uuid/marshal.go b/vendor/github.com/google/uuid/marshal.go
new file mode 100644
index 0000000..7f9e0c6
--- /dev/null
+++ b/vendor/github.com/google/uuid/marshal.go
@@ -0,0 +1,37 @@
+// Copyright 2016 Google Inc.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package uuid
+
+import "fmt"
+
+// MarshalText implements encoding.TextMarshaler.
+func (uuid UUID) MarshalText() ([]byte, error) {
+	var js [36]byte
+	encodeHex(js[:], uuid)
+	return js[:], nil
+}
+
+// UnmarshalText implements encoding.TextUnmarshaler.
+func (uuid *UUID) UnmarshalText(data []byte) error {
+	id, err := ParseBytes(data)
+	if err == nil {
+		*uuid = id
+	}
+	return err
+}
+
+// MarshalBinary implements encoding.BinaryMarshaler.
+func (uuid UUID) MarshalBinary() ([]byte, error) {
+	return uuid[:], nil
+}
+
+// UnmarshalBinary implements encoding.BinaryUnmarshaler.
+func (uuid *UUID) UnmarshalBinary(data []byte) error {
+	if len(data) != 16 {
+		return fmt.Errorf("invalid UUID (got %d bytes)", len(data))
+	}
+	copy(uuid[:], data)
+	return nil
+}
diff --git a/vendor/github.com/google/uuid/node.go b/vendor/github.com/google/uuid/node.go
new file mode 100644
index 0000000..d651a2b
--- /dev/null
+++ b/vendor/github.com/google/uuid/node.go
@@ -0,0 +1,90 @@
+// Copyright 2016 Google Inc.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package uuid
+
+import (
+	"sync"
+)
+
+var (
+	nodeMu sync.Mutex
+	ifname string  // name of interface being used
+	nodeID [6]byte // hardware for version 1 UUIDs
+	zeroID [6]byte // nodeID with only 0's
+)
+
+// NodeInterface returns the name of the interface from which the NodeID was
+// derived.  The interface "user" is returned if the NodeID was set by
+// SetNodeID.
+func NodeInterface() string {
+	defer nodeMu.Unlock()
+	nodeMu.Lock()
+	return ifname
+}
+
+// SetNodeInterface selects the hardware address to be used for Version 1 UUIDs.
+// If name is "" then the first usable interface found will be used or a random
+// Node ID will be generated.  If a named interface cannot be found then false
+// is returned.
+//
+// SetNodeInterface never fails when name is "".
+func SetNodeInterface(name string) bool {
+	defer nodeMu.Unlock()
+	nodeMu.Lock()
+	return setNodeInterface(name)
+}
+
+func setNodeInterface(name string) bool {
+	iname, addr := getHardwareInterface(name) // null implementation for js
+	if iname != "" && addr != nil {
+		ifname = iname
+		copy(nodeID[:], addr)
+		return true
+	}
+
+	// We found no interfaces with a valid hardware address.  If name
+	// does not specify a specific interface generate a random Node ID
+	// (section 4.1.6)
+	if name == "" {
+		ifname = "random"
+		randomBits(nodeID[:])
+		return true
+	}
+	return false
+}
+
+// NodeID returns a slice of a copy of the current Node ID, setting the Node ID
+// if not already set.
+func NodeID() []byte {
+	defer nodeMu.Unlock()
+	nodeMu.Lock()
+	if nodeID == zeroID {
+		setNodeInterface("")
+	}
+	nid := nodeID
+	return nid[:]
+}
+
+// SetNodeID sets the Node ID to be used for Version 1 UUIDs.  The first 6 bytes
+// of id are used.  If id is less than 6 bytes then false is returned and the
+// Node ID is not set.
+func SetNodeID(id []byte) bool {
+	if len(id) < 6 {
+		return false
+	}
+	defer nodeMu.Unlock()
+	nodeMu.Lock()
+	copy(nodeID[:], id)
+	ifname = "user"
+	return true
+}
+
+// NodeID returns the 6 byte node id encoded in uuid.  It returns nil if uuid is
+// not valid.  The NodeID is only well defined for version 1 and 2 UUIDs.
+func (uuid UUID) NodeID() []byte {
+	var node [6]byte
+	copy(node[:], uuid[10:])
+	return node[:]
+}
diff --git a/vendor/github.com/pborman/uuid/node_js.go b/vendor/github.com/google/uuid/node_js.go
index 24b78ed..24b78ed 100644
--- a/vendor/github.com/pborman/uuid/node_js.go
+++ b/vendor/github.com/google/uuid/node_js.go
diff --git a/vendor/github.com/pborman/uuid/node_net.go b/vendor/github.com/google/uuid/node_net.go
index 330b544..0cbbcdd 100644
--- a/vendor/github.com/pborman/uuid/node_net.go
+++ b/vendor/github.com/google/uuid/node_net.go
@@ -26,10 +26,7 @@ func getHardwareInterface(name string) (string, []byte) {
 	}
 	for _, ifs := range interfaces {
 		if len(ifs.HardwareAddr) >= 6 && (name == "" || name == ifs.Name) {
-			if setNodeID(ifs.HardwareAddr) {
-				ifname = ifs.Name
-				return ifname, nodeID
-			}
+			return ifs.Name, ifs.HardwareAddr
 		}
 	}
 	return "", nil
diff --git a/vendor/github.com/google/uuid/sql.go b/vendor/github.com/google/uuid/sql.go
new file mode 100644
index 0000000..f326b54
--- /dev/null
+++ b/vendor/github.com/google/uuid/sql.go
@@ -0,0 +1,59 @@
+// Copyright 2016 Google Inc.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package uuid
+
+import (
+	"database/sql/driver"
+	"fmt"
+)
+
+// Scan implements sql.Scanner so UUIDs can be read from databases transparently
+// Currently, database types that map to string and []byte are supported. Please
+// consult database-specific driver documentation for matching types.
+func (uuid *UUID) Scan(src interface{}) error {
+	switch src := src.(type) {
+	case nil:
+		return nil
+
+	case string:
+		// if an empty UUID comes from a table, we return a null UUID
+		if src == "" {
+			return nil
+		}
+
+		// see Parse for required string format
+		u, err := Parse(src)
+		if err != nil {
+			return fmt.Errorf("Scan: %v", err)
+		}
+
+		*uuid = u
+
+	case []byte:
+		// if an empty UUID comes from a table, we return a null UUID
+		if len(src) == 0 {
+			return nil
+		}
+
+		// assumes a simple slice of bytes if 16 bytes
+		// otherwise attempts to parse
+		if len(src) != 16 {
+			return uuid.Scan(string(src))
+		}
+		copy((*uuid)[:], src)
+
+	default:
+		return fmt.Errorf("Scan: unable to scan type %T into UUID", src)
+	}
+
+	return nil
+}
+
+// Value implements sql.Valuer so that UUIDs can be written to databases
+// transparently. Currently, UUIDs map to strings. Please consult
+// database-specific driver documentation for matching types.
+func (uuid UUID) Value() (driver.Value, error) {
+	return uuid.String(), nil
+}
diff --git a/vendor/github.com/google/uuid/time.go b/vendor/github.com/google/uuid/time.go
new file mode 100644
index 0000000..e6ef06c
--- /dev/null
+++ b/vendor/github.com/google/uuid/time.go
@@ -0,0 +1,123 @@
+// Copyright 2016 Google Inc.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package uuid
+
+import (
+	"encoding/binary"
+	"sync"
+	"time"
+)
+
+// A Time represents a time as the number of 100's of nanoseconds since 15 Oct
+// 1582.
+type Time int64
+
+const (
+	lillian    = 2299160          // Julian day of 15 Oct 1582
+	unix       = 2440587          // Julian day of 1 Jan 1970
+	epoch      = unix - lillian   // Days between epochs
+	g1582      = epoch * 86400    // seconds between epochs
+	g1582ns100 = g1582 * 10000000 // 100s of a nanoseconds between epochs
+)
+
+var (
+	timeMu   sync.Mutex
+	lasttime uint64 // last time we returned
+	clockSeq uint16 // clock sequence for this run
+
+	timeNow = time.Now // for testing
+)
+
+// UnixTime converts t the number of seconds and nanoseconds using the Unix
+// epoch of 1 Jan 1970.
+func (t Time) UnixTime() (sec, nsec int64) {
+	sec = int64(t - g1582ns100)
+	nsec = (sec % 10000000) * 100
+	sec /= 10000000
+	return sec, nsec
+}
+
+// GetTime returns the current Time (100s of nanoseconds since 15 Oct 1582) and
+// clock sequence as well as adjusting the clock sequence as needed.  An error
+// is returned if the current time cannot be determined.
+func GetTime() (Time, uint16, error) {
+	defer timeMu.Unlock()
+	timeMu.Lock()
+	return getTime()
+}
+
+func getTime() (Time, uint16, error) {
+	t := timeNow()
+
+	// If we don't have a clock sequence already, set one.
+	if clockSeq == 0 {
+		setClockSequence(-1)
+	}
+	now := uint64(t.UnixNano()/100) + g1582ns100
+
+	// If time has gone backwards with this clock sequence then we
+	// increment the clock sequence
+	if now <= lasttime {
+		clockSeq = ((clockSeq + 1) & 0x3fff) | 0x8000
+	}
+	lasttime = now
+	return Time(now), clockSeq, nil
+}
+
+// ClockSequence returns the current clock sequence, generating one if not
+// already set.  The clock sequence is only used for Version 1 UUIDs.
+//
+// The uuid package does not use global static storage for the clock sequence or
+// the last time a UUID was generated.  Unless SetClockSequence is used, a new
+// random clock sequence is generated the first time a clock sequence is
+// requested by ClockSequence, GetTime, or NewUUID.  (section 4.2.1.1)
+func ClockSequence() int {
+	defer timeMu.Unlock()
+	timeMu.Lock()
+	return clockSequence()
+}
+
+func clockSequence() int {
+	if clockSeq == 0 {
+		setClockSequence(-1)
+	}
+	return int(clockSeq & 0x3fff)
+}
+
+// SetClockSequence sets the clock sequence to the lower 14 bits of seq.  Setting to
+// -1 causes a new sequence to be generated.
+func SetClockSequence(seq int) {
+	defer timeMu.Unlock()
+	timeMu.Lock()
+	setClockSequence(seq)
+}
+
+func setClockSequence(seq int) {
+	if seq == -1 {
+		var b [2]byte
+		randomBits(b[:]) // clock sequence
+		seq = int(b[0])<<8 | int(b[1])
+	}
+	oldSeq := clockSeq
+	clockSeq = uint16(seq&0x3fff) | 0x8000 // Set our variant
+	if oldSeq != clockSeq {
+		lasttime = 0
+	}
+}
+
+// Time returns the time in 100s of nanoseconds since 15 Oct 1582 encoded in
+// uuid.  The time is only defined for version 1 and 2 UUIDs.
+func (uuid UUID) Time() Time {
+	time := int64(binary.BigEndian.Uint32(uuid[0:4]))
+	time |= int64(binary.BigEndian.Uint16(uuid[4:6])) << 32
+	time |= int64(binary.BigEndian.Uint16(uuid[6:8])&0xfff) << 48
+	return Time(time)
+}
+
+// ClockSequence returns the clock sequence encoded in uuid.
+// The clock sequence is only well defined for version 1 and 2 UUIDs.
+func (uuid UUID) ClockSequence() int {
+	return int(binary.BigEndian.Uint16(uuid[8:10])) & 0x3fff
+}
diff --git a/vendor/github.com/google/uuid/util.go b/vendor/github.com/google/uuid/util.go
new file mode 100644
index 0000000..5ea6c73
--- /dev/null
+++ b/vendor/github.com/google/uuid/util.go
@@ -0,0 +1,43 @@
+// Copyright 2016 Google Inc.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package uuid
+
+import (
+	"io"
+)
+
+// randomBits completely fills slice b with random data.
+func randomBits(b []byte) {
+	if _, err := io.ReadFull(rander, b); err != nil {
+		panic(err.Error()) // rand should never fail
+	}
+}
+
+// xvalues returns the value of a byte as a hexadecimal digit or 255.
+var xvalues = [256]byte{
+	255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+	255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+	255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+	0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 255, 255, 255, 255, 255, 255,
+	255, 10, 11, 12, 13, 14, 15, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+	255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+	255, 10, 11, 12, 13, 14, 15, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+	255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+	255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+	255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+	255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+	255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+	255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+	255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+	255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+	255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+}
+
+// xtob converts hex characters x1 and x2 into a byte.
+func xtob(x1, x2 byte) (byte, bool) {
+	b1 := xvalues[x1]
+	b2 := xvalues[x2]
+	return (b1 << 4) | b2, b1 != 255 && b2 != 255
+}
diff --git a/vendor/github.com/google/uuid/uuid.go b/vendor/github.com/google/uuid/uuid.go
new file mode 100644
index 0000000..524404c
--- /dev/null
+++ b/vendor/github.com/google/uuid/uuid.go
@@ -0,0 +1,245 @@
+// Copyright 2018 Google Inc.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package uuid
+
+import (
+	"bytes"
+	"crypto/rand"
+	"encoding/hex"
+	"errors"
+	"fmt"
+	"io"
+	"strings"
+)
+
+// A UUID is a 128 bit (16 byte) Universal Unique IDentifier as defined in RFC
+// 4122.
+type UUID [16]byte
+
+// A Version represents a UUID's version.
+type Version byte
+
+// A Variant represents a UUID's variant.
+type Variant byte
+
+// Constants returned by Variant.
+const (
+	Invalid   = Variant(iota) // Invalid UUID
+	RFC4122                   // The variant specified in RFC4122
+	Reserved                  // Reserved, NCS backward compatibility.
+	Microsoft                 // Reserved, Microsoft Corporation backward compatibility.
+	Future                    // Reserved for future definition.
+)
+
+var rander = rand.Reader // random function
+
+// Parse decodes s into a UUID or returns an error.  Both the standard UUID
+// forms of xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx and
+// urn:uuid:xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx are decoded as well as the
+// Microsoft encoding {xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx} and the raw hex
+// encoding: xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx.
+func Parse(s string) (UUID, error) {
+	var uuid UUID
+	switch len(s) {
+	// xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
+	case 36:
+
+	// urn:uuid:xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
+	case 36 + 9:
+		if strings.ToLower(s[:9]) != "urn:uuid:" {
+			return uuid, fmt.Errorf("invalid urn prefix: %q", s[:9])
+		}
+		s = s[9:]
+
+	// {xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx}
+	case 36 + 2:
+		s = s[1:]
+
+	// xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
+	case 32:
+		var ok bool
+		for i := range uuid {
+			uuid[i], ok = xtob(s[i*2], s[i*2+1])
+			if !ok {
+				return uuid, errors.New("invalid UUID format")
+			}
+		}
+		return uuid, nil
+	default:
+		return uuid, fmt.Errorf("invalid UUID length: %d", len(s))
+	}
+	// s is now at least 36 bytes long
+	// it must be of the form  xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
+	if s[8] != '-' || s[13] != '-' || s[18] != '-' || s[23] != '-' {
+		return uuid, errors.New("invalid UUID format")
+	}
+	for i, x := range [16]int{
+		0, 2, 4, 6,
+		9, 11,
+		14, 16,
+		19, 21,
+		24, 26, 28, 30, 32, 34} {
+		v, ok := xtob(s[x], s[x+1])
+		if !ok {
+			return uuid, errors.New("invalid UUID format")
+		}
+		uuid[i] = v
+	}
+	return uuid, nil
+}
+
+// ParseBytes is like Parse, except it parses a byte slice instead of a string.
+func ParseBytes(b []byte) (UUID, error) {
+	var uuid UUID
+	switch len(b) {
+	case 36: // xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
+	case 36 + 9: // urn:uuid:xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
+		if !bytes.Equal(bytes.ToLower(b[:9]), []byte("urn:uuid:")) {
+			return uuid, fmt.Errorf("invalid urn prefix: %q", b[:9])
+		}
+		b = b[9:]
+	case 36 + 2: // {xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx}
+		b = b[1:]
+	case 32: // xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
+		var ok bool
+		for i := 0; i < 32; i += 2 {
+			uuid[i/2], ok = xtob(b[i], b[i+1])
+			if !ok {
+				return uuid, errors.New("invalid UUID format")
+			}
+		}
+		return uuid, nil
+	default:
+		return uuid, fmt.Errorf("invalid UUID length: %d", len(b))
+	}
+	// s is now at least 36 bytes long
+	// it must be of the form  xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
+	if b[8] != '-' || b[13] != '-' || b[18] != '-' || b[23] != '-' {
+		return uuid, errors.New("invalid UUID format")
+	}
+	for i, x := range [16]int{
+		0, 2, 4, 6,
+		9, 11,
+		14, 16,
+		19, 21,
+		24, 26, 28, 30, 32, 34} {
+		v, ok := xtob(b[x], b[x+1])
+		if !ok {
+			return uuid, errors.New("invalid UUID format")
+		}
+		uuid[i] = v
+	}
+	return uuid, nil
+}
+
+// MustParse is like Parse but panics if the string cannot be parsed.
+// It simplifies safe initialization of global variables holding compiled UUIDs.
+func MustParse(s string) UUID {
+	uuid, err := Parse(s)
+	if err != nil {
+		panic(`uuid: Parse(` + s + `): ` + err.Error())
+	}
+	return uuid
+}
+
+// FromBytes creates a new UUID from a byte slice. Returns an error if the slice
+// does not have a length of 16. The bytes are copied from the slice.
+func FromBytes(b []byte) (uuid UUID, err error) {
+	err = uuid.UnmarshalBinary(b)
+	return uuid, err
+}
+
+// Must returns uuid if err is nil and panics otherwise.
+func Must(uuid UUID, err error) UUID {
+	if err != nil {
+		panic(err)
+	}
+	return uuid
+}
+
+// String returns the string form of uuid, xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
+// , or "" if uuid is invalid.
+func (uuid UUID) String() string {
+	var buf [36]byte
+	encodeHex(buf[:], uuid)
+	return string(buf[:])
+}
+
+// URN returns the RFC 2141 URN form of uuid,
+// urn:uuid:xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx,  or "" if uuid is invalid.
+func (uuid UUID) URN() string {
+	var buf [36 + 9]byte
+	copy(buf[:], "urn:uuid:")
+	encodeHex(buf[9:], uuid)
+	return string(buf[:])
+}
+
+func encodeHex(dst []byte, uuid UUID) {
+	hex.Encode(dst, uuid[:4])
+	dst[8] = '-'
+	hex.Encode(dst[9:13], uuid[4:6])
+	dst[13] = '-'
+	hex.Encode(dst[14:18], uuid[6:8])
+	dst[18] = '-'
+	hex.Encode(dst[19:23], uuid[8:10])
+	dst[23] = '-'
+	hex.Encode(dst[24:], uuid[10:])
+}
+
+// Variant returns the variant encoded in uuid.
+func (uuid UUID) Variant() Variant {
+	switch {
+	case (uuid[8] & 0xc0) == 0x80:
+		return RFC4122
+	case (uuid[8] & 0xe0) == 0xc0:
+		return Microsoft
+	case (uuid[8] & 0xe0) == 0xe0:
+		return Future
+	default:
+		return Reserved
+	}
+}
+
+// Version returns the version of uuid.
+func (uuid UUID) Version() Version {
+	return Version(uuid[6] >> 4)
+}
+
+func (v Version) String() string {
+	if v > 15 {
+		return fmt.Sprintf("BAD_VERSION_%d", v)
+	}
+	return fmt.Sprintf("VERSION_%d", v)
+}
+
+func (v Variant) String() string {
+	switch v {
+	case RFC4122:
+		return "RFC4122"
+	case Reserved:
+		return "Reserved"
+	case Microsoft:
+		return "Microsoft"
+	case Future:
+		return "Future"
+	case Invalid:
+		return "Invalid"
+	}
+	return fmt.Sprintf("BadVariant%d", int(v))
+}
+
+// SetRand sets the random number generator to r, which implements io.Reader.
+// If r.Read returns an error when the package requests random data then
+// a panic will be issued.
+//
+// Calling SetRand with nil sets the random number generator to the default
+// generator.
+func SetRand(r io.Reader) {
+	if r == nil {
+		rander = rand.Reader
+		return
+	}
+	rander = r
+}
diff --git a/vendor/github.com/google/uuid/version1.go b/vendor/github.com/google/uuid/version1.go
new file mode 100644
index 0000000..199a1ac
--- /dev/null
+++ b/vendor/github.com/google/uuid/version1.go
@@ -0,0 +1,44 @@
+// Copyright 2016 Google Inc.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package uuid
+
+import (
+	"encoding/binary"
+)
+
+// NewUUID returns a Version 1 UUID based on the current NodeID and clock
+// sequence, and the current time.  If the NodeID has not been set by SetNodeID
+// or SetNodeInterface then it will be set automatically.  If the NodeID cannot
+// be set NewUUID returns nil.  If clock sequence has not been set by
+// SetClockSequence then it will be set automatically.  If GetTime fails to
+// return the current NewUUID returns nil and an error.
+//
+// In most cases, New should be used.
+func NewUUID() (UUID, error) {
+	nodeMu.Lock()
+	if nodeID == zeroID {
+		setNodeInterface("")
+	}
+	nodeMu.Unlock()
+
+	var uuid UUID
+	now, seq, err := GetTime()
+	if err != nil {
+		return uuid, err
+	}
+
+	timeLow := uint32(now & 0xffffffff)
+	timeMid := uint16((now >> 32) & 0xffff)
+	timeHi := uint16((now >> 48) & 0x0fff)
+	timeHi |= 0x1000 // Version 1
+
+	binary.BigEndian.PutUint32(uuid[0:], timeLow)
+	binary.BigEndian.PutUint16(uuid[4:], timeMid)
+	binary.BigEndian.PutUint16(uuid[6:], timeHi)
+	binary.BigEndian.PutUint16(uuid[8:], seq)
+	copy(uuid[10:], nodeID[:])
+
+	return uuid, nil
+}
diff --git a/vendor/github.com/google/uuid/version4.go b/vendor/github.com/google/uuid/version4.go
new file mode 100644
index 0000000..9ad1aba
--- /dev/null
+++ b/vendor/github.com/google/uuid/version4.go
@@ -0,0 +1,43 @@
+// Copyright 2016 Google Inc.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package uuid
+
+import "io"
+
+// New creates a new random UUID or panics.  New is equivalent to
+// the expression
+//
+//    uuid.Must(uuid.NewRandom())
+func New() UUID {
+	return Must(NewRandom())
+}
+
+// NewRandom returns a Random (Version 4) UUID.
+//
+// The strength of the UUIDs is based on the strength of the crypto/rand
+// package.
+//
+// A note about uniqueness derived from the UUID Wikipedia entry:
+//
+//  Randomly generated UUIDs have 122 random bits.  One's annual risk of being
+//  hit by a meteorite is estimated to be one chance in 17 billion, that
+//  means the probability is about 0.00000000006 (6 × 10−11),
+//  equivalent to the odds of creating a few tens of trillions of UUIDs in a
+//  year and having one duplicate.
+func NewRandom() (UUID, error) {
+	return NewRandomFromReader(rander)
+}
+
+func NewRandomFromReader(r io.Reader) (UUID, error) {
+	var uuid UUID
+	_, err := io.ReadFull(r, uuid[:])
+	if err != nil {
+		return Nil, err
+	}
+	uuid[6] = (uuid[6] & 0x0f) | 0x40 // Version 4
+	uuid[8] = (uuid[8] & 0x3f) | 0x80 // Variant is 10
+	return uuid, nil
+}
+
diff --git a/vendor/github.com/pborman/uuid/README.md b/vendor/github.com/pborman/uuid/README.md
index b0396b2..810ad40 100644
--- a/vendor/github.com/pborman/uuid/README.md
+++ b/vendor/github.com/pborman/uuid/README.md
@@ -3,6 +3,8 @@ This project was automatically exported from code.google.com/p/go-uuid
 # uuid ![build status](https://travis-ci.org/pborman/uuid.svg?branch=master)
 The uuid package generates and inspects UUIDs based on [RFC 4122](http://tools.ietf.org/html/rfc4122) and DCE 1.1: Authentication and Security Services. 
 
+This package now leverages the github.com/google/uuid package (which is based off an earlier version of this package).
+
 ###### Install
 `go get github.com/pborman/uuid`
 
diff --git a/vendor/github.com/pborman/uuid/doc.go b/vendor/github.com/pborman/uuid/doc.go
index d8bd013..727d761 100644
--- a/vendor/github.com/pborman/uuid/doc.go
+++ b/vendor/github.com/pborman/uuid/doc.go
@@ -4,5 +4,10 @@
 
 // The uuid package generates and inspects UUIDs.
 //
-// UUIDs are based on RFC 4122 and DCE 1.1: Authentication and Security Services.
+// UUIDs are based on RFC 4122 and DCE 1.1: Authentication and Security
+// Services.
+//
+// This package is a partial wrapper around the github.com/google/uuid package.
+// This package represents a UUID as []byte while github.com/google/uuid
+// represents a UUID as [16]byte.
 package uuid
diff --git a/vendor/github.com/pborman/uuid/go.mod b/vendor/github.com/pborman/uuid/go.mod
new file mode 100644
index 0000000..099fc7d
--- /dev/null
+++ b/vendor/github.com/pborman/uuid/go.mod
@@ -0,0 +1,3 @@
+module github.com/pborman/uuid
+
+require github.com/google/uuid v1.0.0
diff --git a/vendor/github.com/pborman/uuid/go.sum b/vendor/github.com/pborman/uuid/go.sum
new file mode 100644
index 0000000..db2574a
--- /dev/null
+++ b/vendor/github.com/pborman/uuid/go.sum
@@ -0,0 +1,2 @@
+github.com/google/uuid v1.0.0 h1:b4Gk+7WdP/d3HZH8EJsZpvV7EtDOgaZLtnaNGIu1adA=
+github.com/google/uuid v1.0.0/go.mod h1:TIyPZe4MgqvfeYDBFedMoGGpEw/LqOeaOT+nhxU+yHo=
diff --git a/vendor/github.com/pborman/uuid/marshal.go b/vendor/github.com/pborman/uuid/marshal.go
index 6621dd5..35b8935 100644
--- a/vendor/github.com/pborman/uuid/marshal.go
+++ b/vendor/github.com/pborman/uuid/marshal.go
@@ -7,6 +7,8 @@ package uuid
 import (
 	"errors"
 	"fmt"
+
+	guuid "github.com/google/uuid"
 )
 
 // MarshalText implements encoding.TextMarshaler.
@@ -60,11 +62,11 @@ func (u Array) MarshalText() ([]byte, error) {
 
 // UnmarshalText implements encoding.TextUnmarshaler.
 func (u *Array) UnmarshalText(data []byte) error {
-	id := Parse(string(data))
-	if id == nil {
-		return errors.New("invalid UUID")
+	id, err := guuid.ParseBytes(data)
+	if err != nil {
+		return err
 	}
-	*u = id.Array()
+	*u = Array(id)
 	return nil
 }
 
diff --git a/vendor/github.com/pborman/uuid/node.go b/vendor/github.com/pborman/uuid/node.go
index f522385..e524e01 100644
--- a/vendor/github.com/pborman/uuid/node.go
+++ b/vendor/github.com/pborman/uuid/node.go
@@ -5,22 +5,14 @@
 package uuid
 
 import (
-	"sync"
-)
-
-var (
-	nodeMu sync.Mutex
-	ifname string // name of interface being used
-	nodeID []byte // hardware for version 1 UUIDs
+	guuid "github.com/google/uuid"
 )
 
 // NodeInterface returns the name of the interface from which the NodeID was
 // derived.  The interface "user" is returned if the NodeID was set by
 // SetNodeID.
 func NodeInterface() string {
-	defer nodeMu.Unlock()
-	nodeMu.Lock()
-	return ifname
+	return guuid.NodeInterface()
 }
 
 // SetNodeInterface selects the hardware address to be used for Version 1 UUIDs.
@@ -30,67 +22,20 @@ func NodeInterface() string {
 //
 // SetNodeInterface never fails when name is "".
 func SetNodeInterface(name string) bool {
-	defer nodeMu.Unlock()
-	nodeMu.Lock()
-	return setNodeInterface(name)
-}
-
-func setNodeInterface(name string) bool {
-
-	iname, addr := getHardwareInterface(name) // null implementation for js
-	if iname != "" && setNodeID(addr) {
-		ifname = iname
-		return true
-	}
-
-	// We found no interfaces with a valid hardware address.  If name
-	// does not specify a specific interface generate a random Node ID
-	// (section 4.1.6)
-	if name == "" {
-		if nodeID == nil {
-			nodeID = make([]byte, 6)
-		}
-		randomBits(nodeID)
-		return true
-	}
-	return false
+	return guuid.SetNodeInterface(name)
 }
 
 // NodeID returns a slice of a copy of the current Node ID, setting the Node ID
 // if not already set.
 func NodeID() []byte {
-	defer nodeMu.Unlock()
-	nodeMu.Lock()
-	if nodeID == nil {
-		setNodeInterface("")
-	}
-	nid := make([]byte, 6)
-	copy(nid, nodeID)
-	return nid
+	return guuid.NodeID()
 }
 
 // SetNodeID sets the Node ID to be used for Version 1 UUIDs.  The first 6 bytes
 // of id are used.  If id is less than 6 bytes then false is returned and the
 // Node ID is not set.
 func SetNodeID(id []byte) bool {
-	defer nodeMu.Unlock()
-	nodeMu.Lock()
-	if setNodeID(id) {
-		ifname = "user"
-		return true
-	}
-	return false
-}
-
-func setNodeID(id []byte) bool {
-	if len(id) < 6 {
-		return false
-	}
-	if nodeID == nil {
-		nodeID = make([]byte, 6)
-	}
-	copy(nodeID, id)
-	return true
+	return guuid.SetNodeID(id)
 }
 
 // NodeID returns the 6 byte node id encoded in uuid.  It returns nil if uuid is
diff --git a/vendor/github.com/pborman/uuid/sql.go b/vendor/github.com/pborman/uuid/sql.go
index d015bfd..929c384 100644
--- a/vendor/github.com/pborman/uuid/sql.go
+++ b/vendor/github.com/pborman/uuid/sql.go
@@ -40,7 +40,9 @@ func (uuid *UUID) Scan(src interface{}) error {
 		// assumes a simple slice of bytes if 16 bytes
 		// otherwise attempts to parse
 		if len(b) == 16 {
-			*uuid = UUID(b)
+			parsed := make([]byte, 16)
+			copy(parsed, b)
+			*uuid = UUID(parsed)
 		} else {
 			u := Parse(string(b))
 
diff --git a/vendor/github.com/pborman/uuid/time.go b/vendor/github.com/pborman/uuid/time.go
index eedf242..7286824 100644
--- a/vendor/github.com/pborman/uuid/time.go
+++ b/vendor/github.com/pborman/uuid/time.go
@@ -6,65 +6,18 @@ package uuid
 
 import (
 	"encoding/binary"
-	"sync"
-	"time"
+
+	guuid "github.com/google/uuid"
 )
 
 // A Time represents a time as the number of 100's of nanoseconds since 15 Oct
 // 1582.
-type Time int64
-
-const (
-	lillian    = 2299160          // Julian day of 15 Oct 1582
-	unix       = 2440587          // Julian day of 1 Jan 1970
-	epoch      = unix - lillian   // Days between epochs
-	g1582      = epoch * 86400    // seconds between epochs
-	g1582ns100 = g1582 * 10000000 // 100s of a nanoseconds between epochs
-)
-
-var (
-	timeMu    sync.Mutex
-	lasttime  uint64 // last time we returned
-	clock_seq uint16 // clock sequence for this run
-
-	timeNow = time.Now // for testing
-)
-
-// UnixTime converts t the number of seconds and nanoseconds using the Unix
-// epoch of 1 Jan 1970.
-func (t Time) UnixTime() (sec, nsec int64) {
-	sec = int64(t - g1582ns100)
-	nsec = (sec % 10000000) * 100
-	sec /= 10000000
-	return sec, nsec
-}
+type Time = guuid.Time
 
 // GetTime returns the current Time (100s of nanoseconds since 15 Oct 1582) and
 // clock sequence as well as adjusting the clock sequence as needed.  An error
 // is returned if the current time cannot be determined.
-func GetTime() (Time, uint16, error) {
-	defer timeMu.Unlock()
-	timeMu.Lock()
-	return getTime()
-}
-
-func getTime() (Time, uint16, error) {
-	t := timeNow()
-
-	// If we don't have a clock sequence already, set one.
-	if clock_seq == 0 {
-		setClockSequence(-1)
-	}
-	now := uint64(t.UnixNano()/100) + g1582ns100
-
-	// If time has gone backwards with this clock sequence then we
-	// increment the clock sequence
-	if now <= lasttime {
-		clock_seq = ((clock_seq + 1) & 0x3fff) | 0x8000
-	}
-	lasttime = now
-	return Time(now), clock_seq, nil
-}
+func GetTime() (Time, uint16, error) { return guuid.GetTime() }
 
 // ClockSequence returns the current clock sequence, generating one if not
 // already set.  The clock sequence is only used for Version 1 UUIDs.
@@ -74,39 +27,11 @@ func getTime() (Time, uint16, error) {
 // clock sequence is generated the first time a clock sequence is requested by
 // ClockSequence, GetTime, or NewUUID.  (section 4.2.1.1) sequence is generated
 // for
-func ClockSequence() int {
-	defer timeMu.Unlock()
-	timeMu.Lock()
-	return clockSequence()
-}
-
-func clockSequence() int {
-	if clock_seq == 0 {
-		setClockSequence(-1)
-	}
-	return int(clock_seq & 0x3fff)
-}
+func ClockSequence() int { return guuid.ClockSequence() }
 
-// SetClockSeq sets the clock sequence to the lower 14 bits of seq.  Setting to
+// SetClockSequence sets the clock sequence to the lower 14 bits of seq.  Setting to
 // -1 causes a new sequence to be generated.
-func SetClockSequence(seq int) {
-	defer timeMu.Unlock()
-	timeMu.Lock()
-	setClockSequence(seq)
-}
-
-func setClockSequence(seq int) {
-	if seq == -1 {
-		var b [2]byte
-		randomBits(b[:]) // clock sequence
-		seq = int(b[0])<<8 | int(b[1])
-	}
-	old_seq := clock_seq
-	clock_seq = uint16(seq&0x3fff) | 0x8000 // Set our variant
-	if old_seq != clock_seq {
-		lasttime = 0
-	}
-}
+func SetClockSequence(seq int) { guuid.SetClockSequence(seq) }
 
 // Time returns the time in 100s of nanoseconds since 15 Oct 1582 encoded in
 // uuid.  It returns false if uuid is not valid.  The time is only well defined
diff --git a/vendor/github.com/pborman/uuid/util.go b/vendor/github.com/pborman/uuid/util.go
index fc8e052..255b5e2 100644
--- a/vendor/github.com/pborman/uuid/util.go
+++ b/vendor/github.com/pborman/uuid/util.go
@@ -4,17 +4,6 @@
 
 package uuid
 
-import (
-	"io"
-)
-
-// randomBits completely fills slice b with random data.
-func randomBits(b []byte) {
-	if _, err := io.ReadFull(rander, b); err != nil {
-		panic(err.Error()) // rand should never fail
-	}
-}
-
 // xvalues returns the value of a byte as a hexadecimal digit or 255.
 var xvalues = [256]byte{
 	255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
diff --git a/vendor/github.com/pborman/uuid/uuid.go b/vendor/github.com/pborman/uuid/uuid.go
index 7c643cf..3370004 100644
--- a/vendor/github.com/pborman/uuid/uuid.go
+++ b/vendor/github.com/pborman/uuid/uuid.go
@@ -8,9 +8,9 @@ import (
 	"bytes"
 	"crypto/rand"
 	"encoding/hex"
-	"fmt"
 	"io"
-	"strings"
+
+	guuid "github.com/google/uuid"
 )
 
 // Array is a pass-by-value UUID that can be used as an effecient key in a map.
@@ -24,7 +24,7 @@ func (uuid Array) UUID() UUID {
 // String returns the string representation of uuid,
 // xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx.
 func (uuid Array) String() string {
-	return uuid.UUID().String()
+	return guuid.UUID(uuid).String()
 }
 
 // A UUID is a 128 bit (16 byte) Universal Unique IDentifier as defined in RFC
@@ -32,18 +32,18 @@ func (uuid Array) String() string {
 type UUID []byte
 
 // A Version represents a UUIDs version.
-type Version byte
+type Version = guuid.Version
 
 // A Variant represents a UUIDs variant.
-type Variant byte
+type Variant = guuid.Variant
 
 // Constants returned by Variant.
 const (
-	Invalid   = Variant(iota) // Invalid UUID
-	RFC4122                   // The variant specified in RFC4122
-	Reserved                  // Reserved, NCS backward compatibility.
-	Microsoft                 // Reserved, Microsoft Corporation backward compatibility.
-	Future                    // Reserved for future definition.
+	Invalid   = guuid.Invalid   // Invalid UUID
+	RFC4122   = guuid.RFC4122   // The variant specified in RFC4122
+	Reserved  = guuid.Reserved  // Reserved, NCS backward compatibility.
+	Microsoft = guuid.Microsoft // Reserved, Microsoft Corporation backward compatibility.
+	Future    = guuid.Future    // Reserved for future definition.
 )
 
 var rander = rand.Reader // random function
@@ -54,35 +54,23 @@ func New() string {
 	return NewRandom().String()
 }
 
-// Parse decodes s into a UUID or returns nil.  Both the UUID form of
-// xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx and
-// urn:uuid:xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx are decoded.
+// Parse decodes s into a UUID or returns nil. See github.com/google/uuid for
+// the formats parsed.
 func Parse(s string) UUID {
-	if len(s) == 36+9 {
-		if strings.ToLower(s[:9]) != "urn:uuid:" {
-			return nil
-		}
-		s = s[9:]
-	} else if len(s) != 36 {
-		return nil
-	}
-	if s[8] != '-' || s[13] != '-' || s[18] != '-' || s[23] != '-' {
-		return nil
+	gu, err := guuid.Parse(s)
+	if err == nil {
+		return gu[:]
 	}
-	var uuid [16]byte
-	for i, x := range [16]int{
-		0, 2, 4, 6,
-		9, 11,
-		14, 16,
-		19, 21,
-		24, 26, 28, 30, 32, 34} {
-		if v, ok := xtob(s[x:]); !ok {
-			return nil
-		} else {
-			uuid[i] = v
-		}
+	return nil
+}
+
+// ParseBytes is like Parse, except it parses a byte slice instead of a string.
+func ParseBytes(b []byte) (UUID, error) {
+	gu, err := guuid.ParseBytes(b)
+	if err == nil {
+		return gu[:], nil
 	}
-	return uuid[:]
+	return nil, err
 }
 
 // Equal returns true if uuid1 and uuid2 are equal.
@@ -163,29 +151,6 @@ func (uuid UUID) Version() (Version, bool) {
 	return Version(uuid[6] >> 4), true
 }
 
-func (v Version) String() string {
-	if v > 15 {
-		return fmt.Sprintf("BAD_VERSION_%d", v)
-	}
-	return fmt.Sprintf("VERSION_%d", v)
-}
-
-func (v Variant) String() string {
-	switch v {
-	case RFC4122:
-		return "RFC4122"
-	case Reserved:
-		return "Reserved"
-	case Microsoft:
-		return "Microsoft"
-	case Future:
-		return "Future"
-	case Invalid:
-		return "Invalid"
-	}
-	return fmt.Sprintf("BadVariant%d", int(v))
-}
-
 // SetRand sets the random number generator to r, which implements io.Reader.
 // If r.Read returns an error when the package requests random data then
 // a panic will be issued.
@@ -193,9 +158,5 @@ func (v Variant) String() string {
 // Calling SetRand with nil sets the random number generator to the default
 // generator.
 func SetRand(r io.Reader) {
-	if r == nil {
-		rander = rand.Reader
-		return
-	}
-	rander = r
+	guuid.SetRand(r)
 }
diff --git a/vendor/github.com/pborman/uuid/version1.go b/vendor/github.com/pborman/uuid/version1.go
index 0127eac..7af948d 100644
--- a/vendor/github.com/pborman/uuid/version1.go
+++ b/vendor/github.com/pborman/uuid/version1.go
@@ -5,7 +5,7 @@
 package uuid
 
 import (
-	"encoding/binary"
+	guuid "github.com/google/uuid"
 )
 
 // NewUUID returns a Version 1 UUID based on the current NodeID and clock
@@ -15,27 +15,9 @@ import (
 // SetClockSequence then it will be set automatically.  If GetTime fails to
 // return the current NewUUID returns nil.
 func NewUUID() UUID {
-	if nodeID == nil {
-		SetNodeInterface("")
+	gu, err := guuid.NewUUID()
+	if err == nil {
+		return UUID(gu[:])
 	}
-
-	now, seq, err := GetTime()
-	if err != nil {
-		return nil
-	}
-
-	uuid := make([]byte, 16)
-
-	time_low := uint32(now & 0xffffffff)
-	time_mid := uint16((now >> 32) & 0xffff)
-	time_hi := uint16((now >> 48) & 0x0fff)
-	time_hi |= 0x1000 // Version 1
-
-	binary.BigEndian.PutUint32(uuid[0:], time_low)
-	binary.BigEndian.PutUint16(uuid[4:], time_mid)
-	binary.BigEndian.PutUint16(uuid[6:], time_hi)
-	binary.BigEndian.PutUint16(uuid[8:], seq)
-	copy(uuid[10:], nodeID)
-
-	return uuid
+	return nil
 }
diff --git a/vendor/github.com/pborman/uuid/version4.go b/vendor/github.com/pborman/uuid/version4.go
index b3d4a36..767dd0c 100644
--- a/vendor/github.com/pborman/uuid/version4.go
+++ b/vendor/github.com/pborman/uuid/version4.go
@@ -4,12 +4,14 @@
 
 package uuid
 
-// Random returns a Random (Version 4) UUID or panics.
+import guuid "github.com/google/uuid"
+
+// NewRandom returns a Random (Version 4) UUID or panics.
 //
 // The strength of the UUIDs is based on the strength of the crypto/rand
 // package.
 //
-// A note about uniqueness derived from from the UUID Wikipedia entry:
+// A note about uniqueness derived from the UUID Wikipedia entry:
 //
 //  Randomly generated UUIDs have 122 random bits.  One's annual risk of being
 //  hit by a meteorite is estimated to be one chance in 17 billion, that
@@ -17,9 +19,8 @@ package uuid
 //  equivalent to the odds of creating a few tens of trillions of UUIDs in a
 //  year and having one duplicate.
 func NewRandom() UUID {
-	uuid := make([]byte, 16)
-	randomBits([]byte(uuid))
-	uuid[6] = (uuid[6] & 0x0f) | 0x40 // Version 4
-	uuid[8] = (uuid[8] & 0x3f) | 0x80 // Variant is 10
-	return uuid
+	if gu, err := guuid.NewRandom(); err == nil {
+		return UUID(gu[:])
+	}
+	return nil
 }