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

Closes #18

Author: greenkeeper[bot]

package.json

@@ -38,7 +38,7 @@
     "coveralls": "^3.0.0",
     "ghooks": "1.3.2",
     "git-dummy-commit": "^1.3.0",
-    "greenkeeper-postpublish": "1.1.0",
+    "greenkeeper-postpublish": "2.0.0",
     "istanbul": "^0.4.5",
     "jscs": "^3.0.7",
     "jshint": "^2.9.4",