Added a uniqueness check on Artist.name
Only validate Artists when viewing new or creating
Updated routes.
Refactored seeds
Refactored validations and removed the validations that checked join models
Add annotate models
Validations for required fields
if editing a track and the release is removed, the new behavior is that the join record is destroyed using an after save call back.
Added validation constraints so that releases/tracks cannot be associated to the same artist as featured/owned more than once.
Corrected the validation used for ReleaseTrack