Add maintainability badge to README

Author: tomasbasham

README.rst

@@ -1,9 +1,13 @@
-ratelimit |build|
-=================
+ratelimit |build| |maintainability|
+===================================
 
 .. |build| image:: https://travis-ci.org/tomasbasham/ratelimit.svg?branch=master
     :target: https://travis-ci.org/tomasbasham/ratelimit
 
+.. |maintainability| image:: https://api.codeclimate.com/v1/badges/21dc7c529c35cd7ef732/maintainability
+    :target: https://codeclimate.com/github/tomasbasham/ratelimit/maintainability
+    :alt: Maintainability
+
 APIs are a very common way to interact with web services. As the need to
 consume data grows, so does the number of API calls necessary to remain up to
 date with data sources. However many API providers constrain developers from

ratelimit/__init__.py

@@ -21,4 +21,4 @@
     'sleep_and_retry'
 ]
 
-__version__ = '2.2.0'
+__version__ = '2.2.1'