Merge pull request #14 from matplotlib/numfocus-badge

Added Numfocus badge to readme

Author: story645

README.md

@@ -1,6 +1,7 @@
 Matplotlib Backend for Altair Visualization Library
 ==================================================
 [![Join the chat at https://gitter.im/matplotlib/mpl-altair](https://badges.gitter.im/matplotlib/mpl-altair.svg)](https://gitter.im/matplotlib/mpl-altair?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge)
+[![Powered by http://www.numfocus.org](https://img.shields.io/badge/powered%20by-NumFOCUS-orange.svg?style=flat&colorA=E1523D&colorB=007D8A)](http://www.numfocus.org)
 
 # follow these conventions:
 https://matplotlib.org/devel/index.html