Fix auto.js for Node < 4 compatibility

Author: wKovacs64

auto.js

@@ -1,4 +1,4 @@
 // This file can be required in Browserify and Node.js for automatic polyfill
 // To use it:  require('es6-promise/auto');
 'use strict';
-module.exports = require('.').polyfill();
+module.exports = require('./').polyfill();