Add babel-polyfill to dependencies

Author: tonyganch

package.json

@@ -17,6 +17,7 @@
     "node": ">= 0.10.0"
   },
   "dependencies": {
+    "babel-polyfill": "6.23.0",
     "glob": "latest",
     "gonzales-pe": "^3.4.7",
     "minimatch": "3.0.2",

src/core.js

@@ -1,9 +1,8 @@
 'use strict';
 
 
-if (!global._babelPolyfill) {
-  require('babel-polyfill');
-}
+require('babel-polyfill');
+
 let fs = require('fs');
 let gonzales = require('gonzales-pe');
 let minimatch = require('minimatch');