Merge pull request #180 from sarupbanskota/patch-1

Use <code> tag around filename

server/documents/usage/theming.html.eco

@@ -341,7 +341,7 @@ type        : 'Usage'
   </div>
   <div class="no example">
     <h4 class="ui header">Variables Files</h4>
-    <p>A .variables file specifies variables which should be adjusted for a theme.</p>
+    <p>A <code>.variables</code> file specifies variables which should be adjusted for a theme.</p>
     <p>A theme's variable file only needs to include variables which are different for a theme.</p>
   </div>
   <div class="no example">