Add tests for order and order line status change signals.
Add tests for order and order line status change signals.

sasha0/django-oscar,solarissmoke/django-oscar,django-oscar/django-oscar,sasha0/django-oscar,solarissmoke/django-oscar,sonofatailor/django-oscar,django-oscar/django-oscar,sonofatailor/django-oscar,sonofatailor/django-oscar,django-oscar/django-oscar,sonofatailor/django-oscar,sasha0/django-oscar,solarissmoke/django-oscar,sasha0/django-oscar,django-oscar/django-oscar,solarissmoke/django-oscar