overall
- upgrade to latest Ruby and Rails
- perf: submissions index page
- remove all default scopes (which break stuff)
- delete empty files

application_controller
- memoize @school
- default to Wyncode in dev env

submission
- belongs_to :unit is wrong
- distinct_users is slow - ignore it

user
- belongs_to :role is being overriden by self.role
- perf: don't display accepted submissions
- perf: faster way to turn a list of submissions into a list of
  corresponding users

database:
- workaround Rails postgres prepared statements bug:
  https://github.com/rails/rails/issues/15920
- add db names to use in dev env
- some dead tables in schema.rb
- add a migration to populate a default set of roles (which is needed
  for new envs, but not for prod, so I'll have to reverse it there)

routes:
- show school show page in localhost