chore(package): update greenkeeper-postpublish to version 2.0.0

Closes #11

Author: greenkeeper[bot]

package.json

@@ -27,7 +27,7 @@
   ],
   "devDependencies": {
     "commitizen": "2.10.0",
-    "greenkeeper-postpublish": "1.1.0",
+    "greenkeeper-postpublish": "2.0.0",
     "json": "^9.0.4",
     "standard-version": "4.2.0"
   }