chore(package): update babel-preset-es2015 to version 6.6.0

http://greenkeeper.io/

package.json

@@ -39,7 +39,7 @@
     "babel-plugin-transform-class-properties": "6.5.2",
     "babel-plugin-transform-decorators-legacy": "1.3.4",
     "babel-plugin-transform-object-rest-spread": "6.5.0",
-    "babel-preset-es2015": "6.5.0",
+    "babel-preset-es2015": "6.6.0",
     "babel-preset-react": "6.5.0",
     "babel-preset-stage-2": "6.5.0",
     "babel-register": "6.5.2",