message: Add (incomplete) demo for history
diff: <div id="main_content">
  <section class="options">
  + <h2>With history enabled</h2>
  + <ul class="demo_activity">
  + <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>
  + <pre><code>$('a[data-imagelightbox="a"]')
  + .imageLightbox({history: true});
  + </code></pre>
  +
  <h2>With activity indication</h2>
  <ul class="demo_activity">
  <li><a href="images/demo1.jpg" data-imagelightbox="a"><img src="images/thumb1.jpg"></a></li>
  