adding PyPI version badge

Author: Matheus Marchini

README.rst

@@ -5,6 +5,9 @@ Python-PDFKit: HTML to PDF wrapper
 .. image:: https://travis-ci.org/JazzCore/python-pdfkit.png?branch=master
         :target: https://travis-ci.org/JazzCore/python-pdfkit
 
+.. image:: https://badge.fury.io/py/pdfkit.svg
+        :target: http://badge.fury.io/py/pdfkit
+
 Python 2 and 3 wrapper for wkhtmltopdf utility to convert HTML to PDF using Webkit.
 
 This is adapted version of `ruby PDFKit <https://github.com/pdfkit/pdfkit>`_ library, so big thanks to them!