Move flash messages to a partial
Add a comment
Remove useless private methods in application.rb
Use whole Participant object instead of just id

When rendering a list of participant with an edit form, pass a whole Participant object in an instance variable instead of just id.  This will allow to render form errors if save fails.
When updating, use 'save' instead of 'save!' and

render or redirect properly.
Do not validate uniqueness of full name