Add test cases for override_config
Add test cases for override_config

Test usage of override_config in different forms
Ensure flexibility between decorator and context manager

winzard/django-constance,pombredanne/django-constance,jazzband/django-constance,jazzband/django-constance,jazzband/django-constance,jonzlin95/django-constance,jonzlin95/django-constance,thorgate/django-constance,pombredanne/django-constance,jezdez/django-constance,thorgate/django-constance,jezdez/django-constance,APSL/django-constance,dmugtasimov/django-constance,winzard/django-constance,dmugtasimov/django-constance,APSL/django-constance