* Updated for django-mptt 0.5.2
* Fixed typo in the CategoryRelation field in that the foreign key is called 'story'
* Made the order field non-null and default to 0
* Changed the parent foreign key a TreeForeignKey (for 0.5.2)
* Changed requirements to mptt>=0.5.2
* Added a migration for model changes.
Why? ImageField causes hits to storage to fill out certain fields. Added a storage class and width/height fields so it is possible to scale the thumbnails and store them somewhere besides the filesystem.