chore(package): update coveralls to version 2.11.15 (#225)

https://greenkeeper.io/

Author: greenkeeperio-bot

package.json

@@ -46,7 +46,7 @@
     "chalk": "1.1.3",
     "chokidar-cli": "1.2.0",
     "conventional-changelog-cli": "1.2.0",
-    "coveralls": "2.11.14",
+    "coveralls": "2.11.15",
     "cz-conventional-changelog": "1.2.0",
     "diff": "3.0.1",
     "in-publish": "2.0.0",