Change PyPI URL in readme
|PyPI| |Travis| |Gitter| |DOI|
.. |PyPI| image:: https://img.shields.io/pypi/v/folium.svg
- :target: https://pypi.python.org/pypi/folium/
+ :target: https://pypi.org/project/folium
:alt: PyPI Package
.. |Travis| image:: https://travis-ci.org/python-visualization/folium.svg?branch=master
