make jest include polyfills so that it works on node 6

package.json

@@ -57,7 +57,8 @@
       "source-map",
       "denodeify",
       "fbjs",
-      "sinon"
+      "sinon",
+      "core-js"
     ]
   }
 }

scripts/setupJest.js

@@ -9,3 +9,4 @@
 'use strict';
 
 global.Promise = require('promise');
+require('../packages/metro-bundler/build/setupNodePolyfills');