Fix permalinks

So much pain, so little gain. 

This handles the case where a url is a permalink to a hidden comment and makes the following changes: For this case and this case only - render all replies to comments and hide all but the top 3 . In this case, the behaviour to render the 'show more replies' buttons and to handle the 'show more replies' click changes - as the hidden comments are already rendered in the dom. 

Finally, when changing location to the permalinked comment, determine whether or not it is visible and, if not, make that thread visible. 

This link will then work: http://www.theguardian.com/commentisfree/2014/oct/07/why-supermarkets-are-on-the-way-out-aldi-lidl#comment-41935830

As illustrated here: 

![permalink](https://cloud.githubusercontent.com/assets/986155/4591139/6b72565a-5068-11e4-8cf9-0eae99512e98.png)

`slice` is being called on the return value of `getClass`, which I'm guessing is a string