chore(package): update babel-core to version 6.23.1

Closes #300

https://greenkeeper.io/

Author: greenkeeper[bot]

package.json

@@ -42,7 +42,7 @@
     "@types/node": "7.0.5",
     "@types/react": "15.0.9",
     "ava": "0.18.0",
-    "babel-core": "6.21.0",
+    "babel-core": "6.23.1",
     "babel-preset-es2015": "6.18.0",
     "babel-register": "6.18.0",
     "chalk": "1.1.3",