chore(package): update del to version 2.2.1

https://greenkeeper.io/

Author: greenkeeperio-bot

package.json

@@ -55,7 +55,7 @@
     "chai": "3.5.0",
     "conventional-changelog-cli": "1.2.0",
     "coveralls": "2.11.9",
-    "del": "2.2.0",
+    "del": "2.2.1",
     "eslint": "2.13.1",
     "eslint-friendly-formatter": "2.0.5",
     "glob": "7.0.5",