update urfave/cli v1.22.1, go-md2man v2.0.0, blackfriday v2.0.1

This updates urfave/cli and its dependencies to v1.22.1:

- diff for urfave/cli: https://github.com/urfave/cli/compare/v1.22.0...v1.22.1
- diff for go-md2man: https://github.com/cpuguy83/go-md2man/compare/v1.0.10...v2.0.0
- diff for blackfriday: https://github.com/russross/blackfriday/compare/v1.5.2...v2.0.1

Also adds github.com/shurcooL/sanitized_anchor_name as a new dependency, which is
used by russross/blackfriday, but will be removed again in a future update (dependency
is already removed on the v2 branch through russross/blackfriday@919b1f5b9b

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

vendor/github.com/russross/blackfriday/v2/esc.go

@@ -0,0 +1,34 @@
+package blackfriday
+
+import (
+	"html"
+	"io"
+)
+
+var htmlEscaper = [256][]byte{
+	'&': []byte("&"),
+	'<': []byte("&lt;"),
+	'>': []byte("&gt;"),
+	'"': []byte("&quot;"),
+}
+
+func escapeHTML(w io.Writer, s []byte) {
+	var start, end int
+	for end < len(s) {
+		escSeq := htmlEscaper[s[end]]
+		if escSeq != nil {
+			w.Write(s[start:end])
+			w.Write(escSeq)
+			start = end + 1
+		}
+		end++
+	}
+	if start < len(s) && end <= len(s) {
+		w.Write(s[start:end])
+	}
+}
+
+func escLink(w io.Writer, text []byte) {
+	unesc := html.UnescapeString(string(text))
+	escapeHTML(w, []byte(unesc))
+}