Merge pull request #61 from KnisterPeter/greenkeeper-babel-core-6.6.4

Update babel-core to version 6.6.4 🚀

Author: KnisterPeter

package.json

@@ -35,7 +35,7 @@
   },
   "license": "MIT",
   "devDependencies": {
-    "babel-core": "6.6.0",
+    "babel-core": "6.6.4",
     "babel-preset-es2015": "6.6.0",
     "babel-register": "6.6.0",
     "chai": "3.5.0",