basic roles

1. add roles to User and InstanceUser model

2. add two tests and refine existing tests, remove should statement ( http://betterspecs.org/#should )
like I said. what is the "real" database is dependent on you. If you have modified `schema.rb`, and you do a `db:reset`, then you'll get the same database. I would have the database table columns organised in a logical and consistent manner because people _do_ examine the database.