Removed unnecessary import
Show empty repos
Added a generic foreign key to Repositories to point to the repo's owner

Hopefully this makes it easier to tie into the siggame site...

Also updated the guardian and repo fixtures by using the --natural
option for dumpdata. The docs say it's a good idea to do with generic
relations.
Moved guardian fixtures to make loaddata happy
Installed celery
Move archivable directories to /tmp/ before running tar.

It frees up space in repos/
Moved pre_save and post_delete duties to celery tasks

There are some race conditions that come up... those need to be dealt
with. In the meantime, we can take advantage of asynchronous cloning
and stuff. Competitors won't be deleting their own repositories, and
repos have to have unique names. It'll be fine for now.

Famous last words.
Show a "not ready" page if a clone isn't finished.
Merge branch 'feature/celery' into develop
Added south migrations