Added ATOMIC_REQUESTS=True to default DB setup

Quoting Two Scoops of Django:
> Use `ATOMIC_REQUESTS` as long as the performance overhead is bearable. That
> means "forever" on most sites.

{{cookiecutter.repo_name}}/{{cookiecutter.repo_name}}/config/common.py

@@ -264,4 +264,8 @@ class Common(Configuration):
     }
     # END LOGGING CONFIGURATION
 
+    @classmethod
+    def post_setup(cls):
+        cls.DATABASES['default']['ATOMIC_REQUESTS'] = True
+
     # Your common stuff: Below this line define 3rd party library settings