Update README.md

Add pypi package badge

README.md

@@ -1,5 +1,7 @@
 # python-outbreak-info
 
+[![PyPI version](https://badge.fury.io/py/python-outbreak-info.svg)](https://badge.fury.io/py/python-outbreak-info)
+
 Welcome to the python package for [outbreak.info](https://outbreak.info/)!
 
 [Outbreak.info](https://outbreak.info/) is a platform from the [Hughes](https://www.scripps.edu/faculty/hughes/), [Su](https://sulab.org/), [Wu](https://wulab.io/), and [Andersen](https://andersen-lab.com/) labs at Scripps Research for the unification and exploration of SARS-CoV-2 genomic and epidemiology data. It's powered by data provided by [GISAID](https://gisaid.org/).