message: Fix demo image url
diff: <section class="options">
  <h2>With activity indication</h2>
  <ul class="demo_activity">
  - <li><a href="images/demo1.tif" data-imagelightbox="a"><img src="images/thumb1.jpg"></a></li>
  + <li><a href="images/demo1.jpg" data-imagelightbox="a"><img src="images/thumb1.jpg"></a></li>
  <li><a href="images/demo2.jpg" data-imagelightbox="a"><img src="images/thumb2.jpg"></a></li>
  <li><a href="images/demo3.jpg" data-imagelightbox="a"><img src="images/thumb3.jpg"></a></li>
  </ul>
  