title: Avoid search on element values or attributes with fnFilter
body: <p>I've noticed that the search function not only looks for the visible content but also on the attributes of the elements in the table.</p>
  
  <p>Here's a living example of it with a checkbox and its value: (search for "<em>demo</em>", or "<em>second</em>")
  <a href="http://jsfiddle.net/HEDvf/510/" rel="nofollow">http://jsfiddle.net/HEDvf/510/</a></p>
  
  <p>In my case, i have checkboxes in the datable and they have classes, data-types and values. When the user wants to use the search feature, it also look for all those attributes and that's not really what a filter should use. </p>
  
  <p>Example of my checkbox:</p>
  
  <pre><code>&lt;input type="checkbox" value="demo" class="lookForThis"&gt;
  </code></pre>
  
  <p>Is there any way to avoid this behavior? </p>