extract Executor.isolate
fix my stupidity
try to make description more readable
fix passed? check
make execute return executor
guess this is still better (consider top-level test)
move tests
should also replicate included modules and instance methods

but how do we define instance methods based on the other
instance methods?? currently it seems there's no way to do this
in ruby without some kind of source reflection?
extract Isolate
add the TODO
get the proper stat!
can't yet make isolate work for instance methods :(
fix warning