fix(polyfill): load babel/polyfill if it's not already loaded

package.json

@@ -1,6 +1,6 @@
 {
   "name": "hapi-sequelize-crud",
-  "version": "2.0.8",
+  "version": "2.0.9",
   "description": "Hapi plugin that automatically generates RESTful API for CRUD",
   "main": "build/index.js",
   "config": {

src/index.js

@@ -1,3 +1,7 @@
+if (!global._babelPolyfill) {
+  require('babel/polyfill');
+}
+
 import crud, { associations } from './crud';
 import url from 'url';
 import qs from 'qs';