Removing es6-promise dependency

lib/axios.js

@@ -5,16 +5,6 @@ var utils = require('./utils');
 var dispatchRequest = require('./core/dispatchRequest');
 var InterceptorManager = require('./core/InterceptorManager');
 
-// Polyfill ES6 Promise if needed
-(function () {
-  // webpack is being used to set es6-promise to the native Promise
-  // for the standalone build. It's necessary to make sure polyfill exists.
-  var P = require('es6-promise');
-  if (P && typeof P.polyfill === 'function') {
-    P.polyfill();
-  }
-})();
-
 var axios = module.exports = function axios(config) {
   config = utils.merge({
     method: 'get',