Merge pull request #25 from th0114nd/stderr_printing

Changed the usage printing to stderr if it is not from -h or --help

Author: mboersma

docopt.go

@@ -52,7 +52,7 @@ func Parse(doc string, argv []string, help bool, version string,
 	args, output, err := parse(doc, argv, help, version, optionsFirst)
 	if _, ok := err.(*UserError); ok {
 		// the user gave us bad input
-		fmt.Println(output)
+		fmt.Fprintln(os.Stderr, output)
 		if exitOk {
 			os.Exit(1)
 		}