Updates app.js version.

index.html

     <script src="//code.jquery.com/ui/1.10.4/jquery-ui.js"></script>
     <script src="muc.js?v=5"></script><!-- simple MUC library -->
     <script src="estos_log.js?v=2"></script><!-- simple stanza logger -->
-    <script src="app.js?v=18"></script><!-- application logic -->
+    <script src="app.js?v=19"></script><!-- application logic -->
     <script src="smileys.js?v=1"></script><!-- smiley images -->
     <script src="replacement.js?v=5"></script><!-- link and smiley replacement -->
     <link href="//netdna.bootstrapcdn.com/font-awesome/4.0.3/css/font-awesome.css" rel="stylesheet">