Add Coveralls badge

README.md

@@ -4,6 +4,7 @@ This is pump.io. It's a stream server that does most of what people
 really want from a social network.
 
 [![Build Status](https://travis-ci.org/pump-io/pump.io.svg?branch=master)](http://travis-ci.org/pump-io/pump.io)
+[![Coverage Status](https://coveralls.io/repos/github/pump-io/pump.io/badge.svg?branch=master)](https://coveralls.io/github/pump-io/pump.io?branch=master)
 [![npm](https://img.shields.io/npm/v/pump.io.svg)](https://npmjs.com/package/pump.io)
 [![NSP Status](https://nodesecurity.io/orgs/pumpio/projects/32213bb8-f9a6-4dd0-8fc6-5caa8ea5f8fc/badge)](https://nodesecurity.io/orgs/pumpio/projects/32213bb8-f9a6-4dd0-8fc6-5caa8ea5f8fc)
 [![Greenkeeper badge](https://badges.greenkeeper.io/pump-io/pump.io.svg)](https://greenkeeper.io/)