Move post_save receiver to receivers.py

[paltman]

Will also mean you need to setup an apps.py and import the receivers.py module during the ready method.

Example: https://github.com/pinax/pinax-stripe/blob/master/pinax/stripe/apps.py#L14 and https://github.com/pinax/pinax-stripe/blob/master/pinax/stripe/__init__.py#L4

[grahamu]

@paltman Where are we moving the post_save receiver from? I don't find any post_save handler in the existing pinax-documents project.

[paltman]

@grahamu https://github.com/pinax/pinax-documents/blob/master/pinax/documents/models.py#L319

[grahamu]

Thanks! No idea why my IDE search didn't find that, but now it does. Hmmm.