Add better_errors as a development requirement

Add a sofia event fixture

Initial draft of the relations

Fix role validation and tests

Add EventParticipation model

Add participants table skeleton

Format the default layout to my likings

Test for duplicate roles

Don't allow duplicate roles

Don't a allow NULL in Role#name

Keep the schema in sync with the latest migration

Initial sketch of the event model

Keep db/schema.rb under version control

Extract the test db seed code into an own method

Clean up the gems, at least for now