Remove test imports that Django 1.5- required

polymorphic/tests/__init__.py

@@ -414,12 +414,3 @@ class SwappableModel(AbstractModel):
 
 class SwappedModel(AbstractModel):
     pass
-
-
-
-# Import tests
-from .test_admin import *
-from .test_orm import *
-from .test_multidb import *
-from .test_regression import *
-

polymorphic/tests/test_contrib.py

@@ -1,3 +1,5 @@
+from unittest import TestCase
+
 from polymorphic.contrib.guardian import get_polymorphic_base_content_type
 from polymorphic.tests import *  # all models