Add AWS Actors using boto.

Rebased off of master

Still needs:
* wait_until_empty Actor
* Integration tests
Well ... depends on what causes the Actor to exit? If there's an error during the run, then I think a raised exception is ok.
If we introduce a timeout for an actor like Wait, and there's no error, but the infinite loop runs for more than 60 seconds, then I could see how that would return False instead of raising an exception.

Maybe other actors could actually have multiple successful return values, like "CheckIfEmpty" rather than "WaitUntilEmpty".

Again -- up for discussion. I figured here, since we're trying to operate on an ELB, and it's not found -- probably an error.