Internal: Upgraded version of Node.js. See ckeditor/ckeditor5-dev#417.

package.json

@@ -57,7 +57,7 @@
     "webpack-cli": "^3.0.8"
   },
   "engines": {
-    "node": ">=6.0.0",
+    "node": ">=6.9.0",
     "npm": ">=3.0.0"
   },
   "author": "CKSource (http://cksource.com/)",