dispose interaces, use just struct
implement graceful shutdown and wire up ActorContext to Actor.
rename monitor forwarding actor.
kill/terminate should propagate from parent to children.  use set.Do(fund) instead of range for set.Iter().
make ForwardActor#Add,Remove be synchronous.
deleted unused spawn methods
paved godoc and includes some minor modifications.
make parent, children in ActorContext be private.
move parent, child to Actor.  Name holds simple name and introduces CanonicalName()
introduce actorSet.  children's type has been changed to actorSet.
introduce ActorPath