Convert test.py to use the Django 1.4+ execute_from_command_line.

execute_manager deprecated in Django 1.4 and removed in 1.6. Use
the same strategy as manage.py to determine whether to use
execute_manager or execute_from_command_line based upon the Django
version.

https://docs.djangoproject.com/en/1.4/releases/1.4/#django-core-management-execute-manager
Merge pull request #80 from johnpaulett/execute-from-command-line-test-entry

Convert test.py to use the Django 1.4+ execute_from_command_line.

(Merging it so that I can test it with the new travis-based testing-multiple-versions setup I just cooked up)