Reformat usage in Github::Auth::Options

Author: Chris Hunt

lib/github/auth/options.rb

@@ -10,7 +10,8 @@ def initialize
         opts.banner = [
           'usage: gh-auth',
           '[--version]',
-          '[add|remove|list]',
+          '[--list]',
+          '[--add|--remove]',
           '<username>'
         ].join(' ')