Update dependencies

vendor/github.com/gomarkdown/markdown/ast/node.go

@@ -1,5 +1,14 @@
 package ast
 
+// An attribute can be attached to block elements. They are specified as
+// {#id .classs key="value"} where quotes for values are mandatory, multiple
+// key/value pairs are separated by whitespace.
+type Attribute struct {
+	ID      []byte
+	Classes [][]byte
+	Attrs   map[string][]byte
+}
+
 // ListType contains bitwise or'ed flags for list and list item objects.
 type ListType int