fix(package.json): add missing dev-dep babel-polyfill

Author: eddywashere

package.json

@@ -34,6 +34,7 @@
   "devDependencies": {
     "babel-core": "^6.5.2",
     "babel-loader": "^6.2.2",
+    "babel-polyfill": "^6.5.0",
     "babel-preset-es2015": "^6.5.0",
     "babel-preset-react": "^6.5.0",
     "babel-preset-stage-0": "^6.5.0",