Adding code climate badges

Author: joaomdmoura

README.md

@@ -1,6 +1,8 @@
 # ActiveModel::Serializer
 
-[![Build Status](https://travis-ci.org/rails-api/active_model_serializers.svg)](https://travis-ci.org/rails-api/active_model_serializers)
+[![Build Status](https://travis-ci.org/rails-api/active_model_serializers.svg)](https://travis-ci.org/rails-api/active_model_serializers) 
+<a href="https://codeclimate.com/github/rails-api/active_model_serializers"><img src="https://codeclimate.com/github/rails-api/active_model_serializers/badges/gpa.svg" /></a>
+<a href="https://codeclimate.com/github/rails-api/active_model_serializers/coverage"><img src="https://codeclimate.com/github/rails-api/active_model_serializers/badges/coverage.svg" /></a>
 
 _Windows Build Status -_ [![Build status](https://ci.appveyor.com/api/projects/status/x6xdjydutm54gvyt/branch/master?svg=true)](https://ci.appveyor.com/project/joaomdmoura/active-model-serializers/branch/master)