the basic idea is to run nightly checks and send email if problems are
found. it should also support variations on that theme,
e.g. configuring a check to only run on certain weekdays.
i think it only makes sense to have an "opinion" for command line
interface in this project, and we probably need more `wutta`
subcommands too but we'll see.
main motivation for this currently is to allow poser apps to define
their own CLI, in particular e.g. `poser install`
