better handling of optional transformers

bin/6to5/index.js

@@ -36,11 +36,6 @@ commander.on("--help", function(){
 
     _.each(_.keys(obj).sort(), function (key) {
       if (key[0] === "_") return;
-
-      if (obj[key].optional) {
-        key = "[" + key + "]";
-      }
-
       console.log("    - " + key);
     });
 

lib/6to5/file.js

@@ -73,6 +73,10 @@ File.normaliseOptions = function (opts) {
   opts.optional  = util.arrayify(opts.optional);
   opts.loose     = util.arrayify(opts.loose);
 
+  opts.optional = opts.optional.map(function (key) {
+    return "optional." + key;
+  });
+
   if (_.contains(opts.loose, "all")) {
     opts.loose = Object.keys(transform.transformers);
   }