Update tester link to reflect right repository

README.md

-# CodeMirror [![Build Status](https://secure.travis-ci.org/marijnh/CodeMirror2.png?branch=master)](http://travis-ci.org/marijnh/CodeMirror2)
+# CodeMirror [![Build Status](https://secure.travis-ci.org/marijnh/CodeMirror.png?branch=master)](http://travis-ci.org/marijnh/CodeMirror)
 
 CodeMirror is a JavaScript component that provides a code editor in
 the browser. When a mode is available for the language you are coding