[real world uses] adds mscgen.js.org

Author: sverweij

doc/realworld.html

@@ -118,6 +118,7 @@ <h2>CodeMirror real-world uses</h2>
       <li><a href="http://www.iunbug.com/mihtool">MIHTool</a> (iOS web-app debugging tool)</li>
       <li><a href="http://mongo-mapreduce-webbrowser.opensagres.cloudbees.net/">Mongo MapReduce WebBrowser</a></li>
       <li><a href="http://montagestudio.com/">Montage Studio</a> (web app creator suite)</li>
+      <li><a href="http://mscgen.js.org/index.html">mscgen_js</a> (online sequence chart editor)</li>
       <li><a href="http://mvcplayground.apphb.com/">MVC Playground</a></li>
       <li><a href="https://www.my2ndgeneration.com/">My2ndGeneration</a> (social coding)</li>
       <li><a href="http://www.navigatecms.com">Navigate CMS</a></li>