Revert "*: providers and sources -> channels, PolicyModel to PolicyBindingModel that uses custom M2M through"

This reverts commit 7ed3ceb960.

passbook/policies/tests/test_engine.py

@@ -2,10 +2,9 @@
 from django.core.cache import cache
 from django.test import TestCase
 
-from passbook.core.models import User
+from passbook.core.models import Policy, User
 from passbook.policies.dummy.models import DummyPolicy
 from passbook.policies.engine import PolicyEngine
-from passbook.policies.models import Policy
 
 
 class PolicyTestEngine(TestCase):