Fixing the hanging mailbox code.
Merge branch 'feature/haxe3-refactor' of https://github.com/SimonRichardson/funk into feature/haxe3-refactor

Conflicts:
	src/main/haxe/funk/actors/ActorCell.hx
Starting to implement a map.
Fixing the Map to have a string key for now.
Fixing map
Starting to make the mailbox more robust.
Adding the ability to kill off an actor.