Add badge with number of monthly downloads.

README.md

@@ -4,6 +4,7 @@ to have a low barrier to entry.  It should be integrated in your web stack
 easily.
 
 [![Build status](https://travis-ci.org/nvie/rq.svg?branch=master)](https://secure.travis-ci.org/nvie/rq)
+[![Downloads](https://pypip.in/d/rq/badge.svg)](https://pypi.python.org/pypi/rq)
 [![Can I Use Python 3?](https://caniusepython3.com/project/rq.svg)](https://caniusepython3.com/project/rq)
 [![Coverage Status](https://img.shields.io/coveralls/nvie/rq.svg)](https://coveralls.io/r/nvie/rq)