document runXXX for State, Reader, Except

it does not document `MonadWriter`'s `run` functions, because i am not sure what to do about them. i am not sure, why you use a `StateT` instead of a `WriterT`, so i am reluncant to do that. i have not yet played around with `ZoomT`. i think the doc for `runZoom` deserve an example :).

after playing around it a bit more, i might write a few examples in the haddock of `Control.Monad.Classes`.