Run Tests on django-tenant-schemas

**NOT READY FOR MERGE**

There was a problem using this package with `django-tenant-schemas` (bernardopires/django-tenant-schemas#191) so I added a framework to test this package when that one is also active.

I am still currently having an error with those tests, so I have to figure out why it is erroring and if that is an error in django-tenant-schemas or an error in this.