Create and view performances

This feature turned out to be several:
*Create a performance
*View a performance
*View the date create and by whom
*Add multiple customers and multiple partners to a performance
*View all customers and partners associated with a performance
*View a list of all performances by customer

@ChristopherThorsen - please take a look
I've got `  validates :contact_id, presence: true` and `validates :role, presence: true`.  Are those good, or are you suggesting i also validate contact, performance, and user?