Badge for supported python versions (#104)

Author: asherf

README.md

@@ -3,6 +3,8 @@ Export Django monitoring metrics for Prometheus.io
 
 [![PyPI version](https://badge.fury.io/py/django-prometheus.svg)](http://badge.fury.io/py/django-prometheus)
 [![Build Status](https://travis-ci.org/korfuri/django-prometheus.svg?branch=master)](https://travis-ci.org/korfuri/django-prometheus)
+[![PyPi page link -- Python versions](https://img.shields.io/pypi/pyversions/django-prometheus.svg)](https://pypi.python.org/pypi/django-prometheus)
+
 
 ## Usage