Add a release badge

README.md

@@ -1,6 +1,7 @@
 ![PyHELP](./images/pyhelp_banner.png)
 
 [![License: MIT](https://img.shields.io/badge/License-MIT-yellow.svg)](https://opensource.org/licenses/MIT)
+[![Latest release](https://img.shields.io/github/release/cgq-qgc/pyhelp.svg)](https://github.com/cgq-qgc/pyhelp/releases)
 [![Documentation Status](https://readthedocs.org/projects/pyhelp/badge/?version=latest)](http://pyhelp.readthedocs.io)
 [![Build status](https://ci.appveyor.com/api/projects/status/ns6s8x0hkd31ffb3/branch/master?svg=true)](https://ci.appveyor.com/project/jnsebgosselin/pyhelp-rd625/branch/master)
 [![codecov](https://codecov.io/gh/cgq-qgc/pyhelp/branch/master/graph/badge.svg)](https://codecov.io/gh/cgq-qgc/pyhelp)