Update conduit-test
Add one missing foreign key constraint
Return connection trait objects

Instead of returning a concrete postgres transaction, this returns a Connection
trait object for req.tx(). This should hopefully make it a little easier to
migrate (if possible) in the future, but primarily allows us to log all sql
queries for now.
Require Put for /{follow, unfollow}

These write to the database, they shouldn't be Get
Funnel all crate listings through /crates
Send some json back on a 403 unauthorized