add babel-core as dep

Author: verwilst

package.json

@@ -6,6 +6,7 @@
   },
   "devDependencies": {
     "babel": "^6.5.2",
+    "babel-core": "^6.18.2",
     "babel-loader": "^6.2.9",
     "babel-plugin-syntax-jsx": "^6.18.0",
     "babel-preset-es2015": "^6.18.0",