Make a dummy test app

[japsu]

At least a manage.py and settings.py so it's easier to try stuff out.

See Lippukala for an ugly pattern of making a test app for a library.

Though it would not hurt to have the whole django-nexmo project be structured like a Django project, with manage.py and example/settings.py.

When this is finally uploaded into PyPI, it is up to setup.py to declare just the nexmo module and not the example module.