fix(package): update update-notifier to version 2.1.0 (#2)

https://greenkeeper.io/

Author: greenkeeper[bot]

package.json

@@ -26,7 +26,7 @@
     "digitalocean": "^0.9.1",
     "lodash": "^4.15.0",
     "public-ip": "^2.1.0",
-    "update-notifier": "^1.0.3"
+    "update-notifier": "^2.1.0"
   },
   "devDependencies": {
     "mocha": "^3.2.0",