removed TODO
added a rewrite clause that modifies the "share" block of the "AddThis_SharingTool" extension. When using this extension to share a product link on social media, the "ref" parameter will now be appended to the product link. Find out more about this extension here: http://support.addthis.com/customer/portal/articles/381234-addthis-for-magento#.UpC02GRXmjE