Django1.5

Here are the changes needed to use django 1.5

Don't pull right away, I think the mailing list should be made aware of this first, I'll write a note.

Heads up: @crawley's archive pull request would also require changes for 1.5. Ie. don't pull both at the same time.
The changes are the same as the ones I already did to existing code calling `call_command`. It has to do with call_command's new behaviour in 1.5.
I'm happy to make those changes btw. I'm just waiting to see which patch is in master first.