[skip] Upgraded to Rails 4.1.6 (15m)

Rails 4.1.6 changed the behavior of serialize …, JSON; I took the opportunity to use a Postgres array column instead
[skip] Updated skylight and rufus-scheduler (2m)
[skip] Upgraded Rails to 4.1.7 (2m)
[fix] Respawned Rufus::Scheduler when Passenger restarts the main process; added a view for checking up on the scheduler thread (1.5h)