fix node require

lib/6to5/register.js

@@ -1,7 +1,7 @@
 require("./polyfill");
 
 var maps = {};
-var node = require("./node");
+var to5  = require("./index");
 var old  = require.extensions[".js"];
 
 // TODO: source maps - Error.prepareStackTrace override
@@ -12,7 +12,7 @@ require.extensions[".es6"] = function (m, filename) {
     return old.apply(this, arguments);
   }
 
-  var result = node.transformFileSync(filename, {
+  var result = to5.transformFileSync(filename, {
     sourceMap: true
   });