Just a wrapper for the barrier/semaphore thing we're doing constantly!
I only applied it in the importer rake tasks for now. There's other
call sites to move over to it, too!
and with a `rails neopets:import` task you can call to do them all at
once!
I'm gonna do some other stuff here too to make `neopets:import` easier
to call all in one go, like prompting for the Neologin cookie just
once at the start.
Note that this changes the cron setup, so you gotta run
`bin/deploy:setup` after this deploys!
