Update markdown parsing library to github.com/gomarkdown/markdown (#944)

vendor/github.com/gomarkdown/markdown/html/esc.go

@@ -0,0 +1,50 @@
+package html
+
+import (
+	"html"
+	"io"
+)
+
+var Escaper = [256][]byte{
+	'&': []byte("&"),
+	'<': []byte("&lt;"),
+	'>': []byte("&gt;"),
+	'"': []byte("&quot;"),
+}
+
+// EscapeHTML writes html-escaped d to w. It escapes &, <, > and " characters.
+func EscapeHTML(w io.Writer, d []byte) {
+	var start, end int
+	n := len(d)
+	for end < n {
+		escSeq := Escaper[d[end]]
+		if escSeq != nil {
+			w.Write(d[start:end])
+			w.Write(escSeq)
+			start = end + 1
+		}
+		end++
+	}
+	if start < n && end <= n {
+		w.Write(d[start:end])
+	}
+}
+
+func escLink(w io.Writer, text []byte) {
+	unesc := html.UnescapeString(string(text))
+	EscapeHTML(w, []byte(unesc))
+}
+
+// Escape writes the text to w, but skips the escape character.
+func Escape(w io.Writer, text []byte) {
+	esc := false
+	for i := 0; i < len(text); i++ {
+		if text[i] == '\\' {
+			esc = !esc
+		}
+		if esc && text[i] == '\\' {
+			continue
+		}
+		w.Write([]byte{text[i]})
+	}
+}