fixed link to Todo-Backend spec site
oh dear! that's embarrassing
implemented actual Postgres backend
made update logic slightly less weird
added semi-reasonable handling of errors
updated README to reflect real database usage
wrote createCallback helper method to reduce code duplication
have I gone too far?
didn't really need a reference to express at all
mentioning by GitHub handle is proper way
yeah, I think that went too far

This reverts commit 53b054956cda3e795e221895464e07d766e940da.