[real-world uses] Add LiveUML

Author: kcwiakala

doc/realworld.html

@@ -119,6 +119,7 @@ <h2>CodeMirror real-world uses</h2>
       <li><a href="http://try.kotlinlang.org">Kotlin</a> (web-based mini-IDE for Kotlin)</li>
       <li><a href="http://lighttable.com/">Light Table</a> (experimental IDE)</li>
       <li><a href="http://liveweave.com/">Liveweave</a> (HTML/CSS/JS scratchpad)</li>
+      <li><a href="https://liveuml.com/">LiveUML</a> (PlantUML online editor)</li>
       <li><a href="https://github.com/TuvaLabs/markdown-delight-editor">Markdown Delight Editor</a> (extensible markdown editor polymer component)</li>
       <li><a href="http://marklighteditor.com/">Marklight editor</a> (lightweight markup editor)</li>
       <li><a href="http://www.mergely.com/">Mergely</a> (interactive diffing)</li>