Add Python and PyPi version badges

Added the badges per our discussions in scikit-learn#6495.

README.rst

@@ -1,6 +1,6 @@
 .. -*- mode: rst -*-
 
-|Travis|_ |AppVeyor|_ |Coveralls|_ |CircleCI|_
+|Travis|_ |AppVeyor|_ |Coveralls|_ |CircleCI|_ |Python27|_ |Python35|_ |PyPi|_ 
 
 .. |Travis| image:: https://api.travis-ci.org/scikit-learn/scikit-learn.svg?branch=master
 .. _Travis: https://travis-ci.org/scikit-learn/scikit-learn
@@ -14,6 +14,14 @@
 .. |CircleCI| image:: https://circleci.com/gh/scikit-learn/scikit-learn/tree/master.svg?style=shield&circle-token=:circle-token
 .. _CircleCI: https://circleci.com/gh/scikit-learn/scikit-learn
 
+.. |Python27| image:: https://img.shields.io/badge/python-2.7-blue.svg
+.. _Python27: https://badge.fury.io/py/scikit-learn
+
+.. |Python35| image:: https://img.shields.io/badge/python-3.5-blue.svg
+.. _Python35: https://badge.fury.io/py/scikit-learn
+
+.. |PyPi| image:: https://badge.fury.io/py/scikit-learn.svg
+.. _PyPi: https://badge.fury.io/py/scikit-learn
 
 scikit-learn
 ============