add pypi badge [ci skip]

Author: st4lk

README.md

@@ -1,7 +1,9 @@
 Affiliate system for django
 ===========================
 
-[![Build Status](https://travis-ci.org/st4lk/django-affiliate.svg?branch=master)](https://travis-ci.org/st4lk/django-affiliate) [![Coverage Status](https://coveralls.io/repos/st4lk/django-affiliate/badge.svg?branch=master)](https://coveralls.io/r/st4lk/django-affiliate?branch=master)
+[![Build Status](https://travis-ci.org/st4lk/django-affiliate.svg?branch=master)](https://travis-ci.org/st4lk/django-affiliate)
+[![Coverage Status](https://coveralls.io/repos/st4lk/django-affiliate/badge.svg?branch=master)](https://coveralls.io/r/st4lk/django-affiliate?branch=master)
+[![Pypi version](https://img.shields.io/pypi/v/django-affiliate.svg)](https://pypi.python.org/pypi/django-affiliate)
 
 
 Affiliate system to reward partners with their visitors payments.