Adds partial support for Django 1.5's custom user models

[rofrankel]

This adds support for Django 1.5's custom user models, though it assumes that either the custom user model is compatible with the contrib.auth User model (this should include nearly all cases in which the custom model is a subclass of AbstractBaseUser).

All current tests pass on both Django 1.5 beta 2 and Django 1.4.3. Any suggestions for new tests?

[meric]

It looks like it also assumes the custom user model has first_name, last_name and email (which Django 1.4 User has), which isn't implemented in AbstractBaseUser.

https://docs.djangoproject.com/en/dev/topics/auth/#django.contrib.auth.models.AbstractBaseUser

[rofrankel]

You are correct - I should have said AbstractUser (which, for some reason, isn't in the docs).

https://github.com/django/django/blob/47e1df896b17aaaa97b73ef64010a7df4ea3d8d6/django/contrib/auth/models.py#L370

[meric]

I see. :)

[matthiask]

Very nice, thanks!

A good step towards solving the issues discussed in #48.

[rofrankel]

My pleasure, thank you for writing Plata!