chore(package): update commitizen to version 4.1.0

Closes #53

Author: greenkeeper[bot]

package.json

@@ -60,7 +60,7 @@
     "babel-preset-es2015": "^6.24.1",
     "babel-preset-stage-2": "^6.24.1",
     "babel-register": "^6.26.0",
-    "commitizen": "^2.9.6",
+    "commitizen": "^4.1.0",
     "conventional-changelog-cli": "^2.0.1",
     "coveralls": "^3.0.0",
     "cz-conventional-changelog": "^2.0.0",