delegate code and opts assurance to File

lib/6to5/file.js

@@ -11,7 +11,7 @@ var _         = require("lodash");
 
 function File(opts) {
   this.opts            = File.normaliseOptions(opts);
-  this.moduleFormatter = this.getModuleFormatter(opts.modules);
+  this.moduleFormatter = this.getModuleFormatter(this.opts.modules);
 
   this.declarations = {};
   this.uids         = {};
@@ -110,6 +110,8 @@ File.prototype.errorWithNode = function (node, msg, Error) {
 };
 
 File.prototype.parse = function (code) {
+  code = (code || "") + "";
+
   var self = this;
 
   this.code = code;

lib/6to5/transformation/transform.js

@@ -5,9 +5,6 @@ var File        = require("../file");
 var _           = require("lodash");
 
 function transform(code, opts) {
-  opts = opts || {};
-  code = (code || "") + "";
-
   var file = new File(opts);
   return file.parse(code);
 }