Don't migrate package migration by default

[driesvints]

At the moment the default migration the package provides still automatically gets migrated when you run php artisan migrate. This shouldn't be the default behavior as you should only need it when you don't want your aggregate roots to be split up into separate tables.

We can't turn off this default behavior just yet because the test suite still expects the table to be present. We'll need to find a way to work around that.