updated python ver badge

Author: jchanvfx

README.md

@@ -1,7 +1,7 @@
 ## NodeGraphQt
 
 [![License: MIT](https://img.shields.io/badge/License-MIT-blue.svg)](LICENSE.md) 
-[![python 3.6+](https://img.shields.io/badge/python-3.6%2B-blue.svg)](https://www.python.org/downloads/)
+[![python 3.7+](https://img.shields.io/badge/python-3.7%2B-blue.svg)](https://www.python.org/downloads/)
 [![PEP8](https://img.shields.io/badge/code%20style-PEP8-green.svg)](https://www.python.org/dev/peps/pep-0008/) 
 [![stability-wip](https://img.shields.io/badge/stability-Work_In_Progress-lightgrey.svg)](https://github.com/orangemug/stability-badges/blob/master/README.md)