Add Code Climate badge to README

Signed-off-by: NChris Aniszczyk <zx@twitter.com>

README.md

 ![Brakeman Logo](http://brakemanscanner.org/images/logo_medium.png)
 
-![Travis CI Status](https://secure.travis-ci.org/presidentbeef/brakeman.png)
+![Travis CI Status](https://secure.travis-ci.org/presidentbeef/brakeman.png) [![Code Climate](https://codeclimate.com/badge.png)](https://codeclimate.com/github/presidentbeef/brakeman)
 
 # Brakeman