Removed @models.permalink in favour of reverse(), which is the recommend way.

https://docs.djangoproject.com/en/1.5/ref/models/instances/#the-permalink-decorator

The Django docs recommend using `django.core.urlresolvers.reverse` instead of `@models.permalink()`. The Django docs have changed this note to a "warning" as of 1.5. `reverse()` has been available and worked the same way in Django since before 1.0, so this is a safe change.