v0.5.4

Upgrade instructions:

• Follow the upgrade instructions for any previous releases.
• Change Biff's :sha value in deps.edn and tasks/deps.edn to 540dc03e6494c2ef6534bcf6023e08215f7cc3dc.

Fixed:

• :db/default operations actually work now (#140 -- thanks @AndreasEdvardsson)

For the record, I do occasionally test new features before shipping them.