Fix _clone signature for Django<1.9

InheritanceQuerySetMixin._clone signature conflicts with django
ValuesQuerySet._clone code which calls super like this:
"c = super(ValuesQuerySet, self)._clone(klass, **kwargs)"

AUTHORS.rst

@@ -35,4 +35,5 @@ sayane
 Tony Aldridge <zaragopha@hotmail.com>
 Travis Swicegood <travis@domain51.com>
 Trey Hunner <trey@treyhunner.com>
+Karl Wan Nan Wo <karl.wnw@gmail.com>
 zyegfryed

model_utils/managers.py

@@ -53,10 +53,13 @@ class InheritanceQuerySetMixin(object):
         new_qs.subclasses = subclasses
         return new_qs
 
-    def _clone(self, **kwargs):
+    def _clone(self, klass=None, setup=False, **kwargs):
         for name in ['subclasses', '_annotated']:
             if hasattr(self, name):
                 kwargs[name] = getattr(self, name)
+        if django.VERSION < (1, 9):
+            kwargs['klass'] = klass
+            kwargs['setup'] = setup
         return super(InheritanceQuerySetMixin, self)._clone(**kwargs)
 
     def annotate(self, *args, **kwargs):

model_utils/tests/tests.py

@@ -763,6 +763,11 @@ class InheritanceManagerTests(TestCase):
                          set(expected_related_names))
 
 
+    def test_filter_on_values_queryset(self):
+        queryset = InheritanceManagerTestChild1.objects.values('id').filter(pk=self.child1.pk)
+        self.assertEqual(list(queryset), [{'id': self.child1.pk}])
+
+
 class InheritanceManagerUsingModelsTests(TestCase):
 
     def setUp(self):