Bust GitHub Camo cache on the PyPI version badge

Appends ?v=5.1.0 to the shields.io badge URLs so GitHub's image proxy
fetches a fresh copy. The proxy was serving a cached 5.0.1 PNG even
though PyPI and shields.io have already updated to 5.1.0.

Author: dbirulia

README.md

@@ -1,7 +1,7 @@
 # veryfi-python
 
-[![PyPI - version](https://img.shields.io/pypi/v/veryfi.svg)](https://pypi.python.org/pypi/veryfi/)
-[![PyPI](https://img.shields.io/pypi/pyversions/veryfi.svg)](https://pypi.python.org/pypi/veryfi)
+[![PyPI - version](https://img.shields.io/pypi/v/veryfi.svg?v=5.1.0)](https://pypi.python.org/pypi/veryfi/)
+[![PyPI](https://img.shields.io/pypi/pyversions/veryfi.svg?v=5.1.0)](https://pypi.python.org/pypi/veryfi)
 [![Code style: black](https://img.shields.io/badge/code%20style-black-000000.svg)](https://github.com/psf/black)
 [![Test](https://github.com/veryfi/veryfi-python/actions/workflows/test.yml/badge.svg?branch=master)](https://github.com/veryfi/veryfi-python/actions/workflows/test.yml)