chore(package): update babel-core to version 6.9.1 (#246)

https://greenkeeper.io/

Author: greenkeeperio-bot

package.json

@@ -48,7 +48,7 @@
   "devDependencies": {
     "axios": "0.9.1",
     "babel-cli": "6.6.5",
-    "babel-core": "6.7.6",
+    "babel-core": "6.9.1",
     "babel-preset-es2015": "6.6.0",
     "babel-preset-stage-2": "6.5.0",
     "chai": "3.5.0",