Extra settings directly into run command

[jonathan-s]

Right here > https://github.com/nephila/django-app-helper/blob/develop/app_helper/runner.py#L9

It would be pretty handy if that function took an argument extra_settings that is a dictionary of all the settings that are extra settings.

That could then be passed to the runner. That way you could circumvent the current hackish way of doing it when necessary and allow for more flexibility to run the tests.

[yakky]

@jonathan-s nice idea! I don't think I have the bandwidth to handle this, but feel free to open a PR, I will happily review & merge it!