chore(package): update commitizen to version 4.0.3

Closes #10

Author: greenkeeper[bot]

package.json

@@ -81,7 +81,7 @@
     "@types/jest": "^23.1.3",
     "@types/node": "^11.9.0",
     "colors": "^1.1.2",
-    "commitizen": "^2.9.6",
+    "commitizen": "^4.0.3",
     "coveralls": "^3.0.0",
     "cross-env": "^5.0.1",
     "cz-conventional-changelog": "^2.0.0",