Update README.md

Author: gkorland

README.md

@@ -2,6 +2,7 @@
 [![PyPI version](https://badge.fury.io/py/redisearch.svg)](https://badge.fury.io/py/redisearch)
 [![CircleCI](https://circleci.com/gh/RediSearch/redisearch-py/tree/master.svg?style=svg)](https://circleci.com/gh/RediSearch/redisearch-py/tree/master)
 [![GitHub issues](https://img.shields.io/github/release/RediSearch/redisearch-py.svg)](https://github.com/RediSearch/redisearch-py/releases/latest)
+[![Codecov](https://codecov.io/gh/RediSearch/redisearch-py/branch/master/graph/badge.svg)](https://codecov.io/gh/RediSearch/redisearch-py)
 
 
 # RediSearch Python Client