Add code climate badge

Author: patrickfav

README.md

@@ -28,6 +28,7 @@ to blindly paste code snippets from
 [![Build Status](https://travis-ci.org/patrickfav/bytes-java.svg?branch=master)](https://travis-ci.org/patrickfav/bytes-java)
 [![Javadocs](https://www.javadoc.io/badge/at.favre.lib/bytes.svg)](https://www.javadoc.io/doc/at.favre.lib/bytes)
 [![Coverage Status](https://coveralls.io/repos/github/patrickfav/bytes-java/badge.svg?branch=master)](https://coveralls.io/github/patrickfav/bytes-java?branch=master)
+[![Maintainability](https://api.codeclimate.com/v1/badges/43b7770f0ee00b85f92a/maintainability)](https://codeclimate.com/github/patrickfav/bytes-java/maintainability)
 
 It's main features include: