chore(package): update babel-core to version 6.3.26

http://greenkeeper.io/

Author: greenkeeperio-bot

package.json

@@ -28,7 +28,7 @@
   },
   "license": "MIT",
   "devDependencies": {
-    "babel-core": "6.3.21",
+    "babel-core": "6.3.26",
     "babel-preset-es2015": "6.3.13",
     "babel-register": "6.3.13",
     "chai": "3.4.1",