chore(package): update babel-core to version 6.11.4 (#2341)

https://greenkeeper.io/

Author: greenkeeperio-bot

package.json

@@ -50,7 +50,7 @@
   },
   "devDependencies": {
     "babel-cli": "6.11.4",
-    "babel-core": "6.10.4",
+    "babel-core": "6.11.4",
     "babel-plugin-syntax-flow": "6.8.0",
     "babel-plugin-transform-flow-strip-types": "6.8.0",
     "babel-preset-es2015": "6.6.0",