docs(readme): change coverage badge to match [ci skip]

Author: bcarroll22

README.md

@@ -6,7 +6,7 @@
 <hr />
 
 [![Build Status](https://travis-ci.org/bcarroll22/rntl.svg?branch=master)](https://travis-ci.org/bcarroll22/rntl)
-[![codecov](https://codecov.io/gh/bcarroll22/rntl/branch/master/graph/badge.svg)](https://codecov.io/gh/bcarroll22/rntl)
+[![Code Coverage](https://img.shields.io/codecov/c/github/bcarroll22/rntl.svg?style=flat-square)](https://codecov.io/github/bcarroll22/rntl)
 [![version](https://img.shields.io/npm/v/rntl.svg?style=flat-square)](https://www.npmjs.com/package/rntl) 
 [![downloads](https://img.shields.io/npm/dm/rntl.svg?style=flat-square)](http://www.npmtrends.com/rntl)
 [![MIT License](https://img.shields.io/npm/l/rntl.svg?style=flat-square)](https://github.com/bcarroll22/rntl/blob/master/LICENSE)