FactoryGirl now treats moods and artists attached to bounties like other properties, and allows them to be overridden by the constructor.
Allow FactoryGirl use in the DB seed file. The seed now generates a realistic volume of users and bounties.

WARNING: since the seed file now creates about 200 users and 3,000
bounties, it now takes a long time to run. On my development machine
seeding the DB takes about 10.