Fix schema migrations for tenants using sql creation

Remove hardcoded reference to 'bithub_development'

I know there is still discussion on the best way to handle excluded models with the tenant creation from SQL feature [here] (https://github.com/influitive/apartment/pull/128#issuecomment-47089646). However, in the meantime it would be great to at least fix this error so the development does not have fatal database messages and works for tenant migrations.

I would have liked to have added some regression tests but I am not sure how to create specs for this code-base. I am open to suggestions. I real integration test would have been to run a new migration somehow and show that it gets recorded in the tenant schema_migrations. I am open to ideas.