Update coveralls badge to develop branch

README.md

@@ -10,7 +10,7 @@ Ethereum PoC-8
 * [![Build Status](http://build.ethdev.com/buildstatusimage?builder=Linux%20Go%20master%20branch)](http://build.ethdev.com:8010/builders/Linux%20Go%20master%20branch/builds/-1) master
 * [![Build Status](http://build.ethdev.com/buildstatusimage?builder=Linux%20Go%20develop%20branch)](http://build.ethdev.com:8010/builders/Linux%20Go%20develop%20branch/builds/-1) develop
 * [![Travis-ci](https://api.travis-ci.org/ethereum/go-ethereum.svg)](https://travis-ci.org/ethereum/go-ethereum) travis-ci
-* [![Coverage Status](https://coveralls.io/repos/ethereum/go-ethereum/badge.png?branch=tests)](https://coveralls.io/r/ethereum/go-ethereum?branch=tests)
+* [![Coverage Status](https://coveralls.io/repos/ethereum/go-ethereum/badge.png?branch=develop)](https://coveralls.io/r/ethereum/go-ethereum?branch=develop)
 
 Ethereum Go Client © 2014 Jeffrey Wilcke.