added ModelSerializer tests

Author: pizzapanther

graphene_django/rest_framework/models.py

@@ -0,0 +1,6 @@
+from django.db import models
+
+
+class MyFakeModel(models.Model):
+    cool_name = models.CharField(max_length=50)
+    created = models.DateTimeField(auto_now_add=True)