Update dependencies

vendor/github.com/alecthomas/chroma/iterator.go

@@ -0,0 +1,43 @@
+package chroma
+
+// An Iterator across tokens.
+//
+// nil will be returned at the end of the Token stream.
+//
+// If an error occurs within an Iterator, it may propagate this in a panic. Formatters should recover.
+type Iterator func() *Token
+
+// Tokens consumes all tokens from the iterator and returns them as a slice.
+func (i Iterator) Tokens() []*Token {
+	out := []*Token{}
+	for t := i(); t != nil; t = i() {
+		out = append(out, t)
+	}
+	return out
+}
+
+// Concaterator concatenates tokens from a series of iterators.
+func Concaterator(iterators ...Iterator) Iterator {
+	return func() *Token {
+		for len(iterators) > 0 {
+			t := iterators[0]()
+			if t != nil {
+				return t
+			}
+			iterators = iterators[1:]
+		}
+		return nil
+	}
+}
+
+// Literator converts a sequence of literal Tokens into an Iterator.
+func Literator(tokens ...*Token) Iterator {
+	return func() (out *Token) {
+		if len(tokens) == 0 {
+			return nil
+		}
+		token := tokens[0]
+		tokens = tokens[1:]
+		return token
+	}
+}