Update README.md

Author: teonbrooks

README.md

@@ -1,6 +1,7 @@
 [![Stories in Ready](https://badge.waffle.io/OpenBCI/openbci-js-sdk.png?label=ready&title=Ready)](https://waffle.io/OpenBCI/openbci-js-sdk)
 [![Join the chat at https://gitter.im/OpenBCI/openbci-js-sdk](https://badges.gitter.im/Join%20Chat.svg)](https://gitter.im/OpenBCI/openbci-js-sdk?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge)
 [![Build Status](https://travis-ci.org/OpenBCI/openbci-js-sdk.svg?branch=master)](https://travis-ci.org/OpenBCI/openbci-js-sdk)
+[![codecov.io](https://codecov.io/github/OpenBCI/openbci-js-sdk/coverage.svg?branch=master)](https://codecov.io/github/OpenBCI/openbci-js-sdk?branch=master)
 
 # openbci-sdk
 
@@ -468,4 +469,4 @@ Testing
 -------
 ```
 npm test
-```
+```