Enable data-options for clearing plugin

Currently its not working to override the default settings in html with the data-options attribute.
With this patch, it works as suggested.

Example:
<ul class="clearing-thumbs small-block-grid-2" data-clearing
        data-options="close_selectors:.clearing-close, div.clearing-blackout, div.visible-img;">
  <li>...</li>
</ul>