..so that other packages can send notifications without making an extra
HTTP request.

Merge branch 'master' of ssh://git.autonomic.zone:2222/autonomic-cooperative/djangoldp-webpushnotification

Let the formatter have its way also.

..by using Django default test client instead of the one from
`rest_framework`.

Also rename `gen_vapid_keys` to `gen_vapid_key`, and merge migrations