Added Django 1.7 migrations

[ondrowan]

I've added initial migration that's required in Django 1.7. I've tried it with most recent RC and it works well. The only problem is that social-auth hadn't used South migrations before and new folder migrations is backwards incompatible for users that still use South. AFAIK the only solution should be to create South migrations folder (eg. south_migrations) and tell users to use following setting:

SOUTH_MIGRATION_MODULES = {
    'social_auth': 'social_auth.path.to.django_app.south_migrations',
}

Or possibly the other way around. Rename this new folder to django_migrations and create new migrations folder with South migrations. But that seems to be more complicated option.

Feedback is welcome as I'm not 100% sure how to handle this situation.

Related to #270.

[ondrowan]

Coincidentally, South 1.0 was released today.

[omab]

Thanks!

Regarding South migrations, they should be added to south_migration folder as suggested IMO.