Add methods to generate comment hashes
Add direct links to comments
Fix missing space
Position the comment better when direct linking.

As per http://nicolasgallagher.com/jump-links-and-viewport-positioning/demo/#method-B, we can't put this on the div with the panel class as it fails due to the border style, so add our own div just for positioning.
Logic fix: both created_date and user_display_name need to be blank in order to return null.
Use the comment's URI as the hash as that way we can guarantee that it exists.
Fix merge conflicts.
Ensure that the unit tests pass when the comment's URI is not set.
Update the comment hash unit tests to take into account the changed algorithm.