docs(readme): add badges to readme

added npm, travis, and codecov badges to readme

README.md

@@ -1,6 +1,8 @@
 ### Commitizen for contributors
 When you commit with Commitizen, you'll be prompted to fill out any required commit fields at commit time. No more waiting until later for a git commit hook to run and reject your commit (though [that](https://github.com/kentcdodds/validate-commit-msg) can still be helpful). No more digging through CONTRIBUTING.md to find what the preferred format is. Get instant feedback on your commit message formatting and be prompted for required fields.
 
+[![travis.ci](https://img.shields.io/travis/commitizen/cz-cli.svg?style=flat-square)](https://travis-ci.org/commitizen/cz-cli) [![codecov.io](https://img.shields.io/codecov/c/github/commitizen/cz-cli.svg?style=flat-square)](https://codecov.io/github/commitizen/cz-cli?branch=master) [![npm monthly downloads](https://img.shields.io/npm/dm/commitizen.svg?style=flat-square)](https://www.npmjs.com/package/commitizen) [![current version](https://img.shields.io/npm/v/commitizen.svg?style=flat-square)](https://www.npmjs.com/package/commitizen)
+
 #### Installing the command line tool
 Installation is as simple as running the following command (add sudo if on OSX/Linux):