chore(package): update babel-preset-es2015 to version 6.13.1 (#313)

https://greenkeeper.io/

Author: greenkeeperio-bot

package.json

@@ -49,7 +49,7 @@
     "axios": "0.13.1",
     "babel-cli": "6.11.4",
     "babel-core": "6.9.1",
-    "babel-preset-es2015": "6.6.0",
+    "babel-preset-es2015": "6.13.1",
     "babel-preset-stage-2": "6.5.0",
     "chai": "3.5.0",
     "codecov.io": "0.1.6",