Update README.rst
Added a binder button to launch jupyter notebook
-|PyPI| |Travis| |Gitter| |DOI|
+|PyPI| |Travis| |Gitter| |DOI| |binder|
.. |PyPI| image:: https://img.shields.io/pypi/v/folium.svg
:target: https://pypi.org/project/folium
:target: https://zenodo.org/badge/latestdoi/18669/python-visualization/folium
:alt: DOI
+.. |binder| image:: https://mybinder.org/badge_logo.svg
+ :target: https://mybinder.org/v2/gh/python-visualization/folium/master?filepath=examples
+
folium
======
