chore(package): update commitizen to version 2.9.0

https://greenkeeper.io/

Author: greenkeeper[bot]

package.json

@@ -25,7 +25,7 @@
     "mkdirp": "^0.5.1"
   },
   "devDependencies": {
-    "commitizen": "^2.8.6",
+    "commitizen": "^2.9.0",
     "coveralls": "^2.11.14",
     "cz-conventional-changelog": "^1.2.0",
     "fs-exists-sync": "^0.1.0",