Adzone should not force contrib.sites on project

[andrewebdev]

Having a adzone depend on sites is not really ideal. This situation comes up with projects that don't really require multi site support (which is probably most projects tbh). Authors may not even include the sites package at all, but will be forced to do so, just so that they can run this app.

I feel that if a client/dev wants site support, they should add this relation to the child models that inherits from Adbase.

[alexkahn]

I've located the dependencies in models.py and managers.py - wouldn't they just need to be deleted? Not sure how one would include sites support, possibly a setting? I am planning on integrating this application into one of my projects so I'd be happy to work the issue.