All specs now passing again after switching to PostgreSQL for
development.  The has_many_inline_spec (which never worked properly) had
some SQLite-3 specific stuff, and it has been removed.  The spec for
WaitingRooms (checking the group formation functionality) used
ActiveRelation's GROUP BY and HAVING in a way that I thought was
portable, but it wasn't; I changed the implementation to just retrieve
all the tasks and manually check for the conditions by counting entries,
rather than using GROUP and HAVING.
Also modified database.yml to only include 'host: localhost' for
postgresql adapter if we're running on Mac OS.