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/urfave/cli/docs.go

@@ -8,7 +8,7 @@ import (
 	"strings"
 	"text/template"
 
-	"github.com/cpuguy83/go-md2man/md2man"
+	"github.com/cpuguy83/go-md2man/v2/md2man"
 )
 
 // ToMarkdown creates a markdown string for the `*App`
@@ -57,6 +57,9 @@ func prepareCommands(commands []Command, level int) []string {
 	coms := []string{}
 	for i := range commands {
 		command := &commands[i]
+		if command.Hidden {
+			continue
+		}
 		usage := ""
 		if command.Usage != "" {
 			usage = command.Usage