Add an "artisan" list for performing migrations and database seeding as part of provisioning.
Will call "php artisan migrate" and "php artisan db:seed" on all projects listed.

Format is:
artisan:
    - project: /home/vagrant/code/path/to/my/laravel/project
    - project: [path to a second project]

Where the project paths point to the root of the Laravel project (where composer.json sits, for example).