Bug fix

Properly using of django.db.models.get_model
Change the name of argument for SinglyBackend.authenticate method to singly_code
Make SinglyProfile fields blank=True
Improve singly backend

Now it will get all profile data directly with authenticate request.
Try to get user by email if in the profile data there is provided email.
If fails to get a user create new one and try to get a profile (in most cases developers catch User create signal and immediatly create profile)
If fail to get profile create new one.