Add a script to generate initial migrations

[kelseyq]

Projects that install your package will generate them automatically, but it's nice to have an initial migration especially if you're deploying using a platform as a service

[browniebroke]

What's the best practice to handle this? Is it done through a manage.py using a basic set of settings? If so, I believe the work from #164 should be enough.

[jonathan-s]

@kelseyq Do you think you could clarify what you think needs to be done?