Provide an option to crash on error / timeout?

[jducoeur]

Suggestion from @jypma on Gitter: it would be in the spirit of Akka if I could set up my RequestM such that, if it errored in some unhandled way, that error got propagated in the receive loop and crashed the Actor.

This needs a bunch of design and thought, but I agree with the spirit of the idea, and it would reduce the likelihood of failures being silently missed.

[jducoeur]

Actually, if we can reliably track which errors get explicitly handled, the ideal would probably be to automatically and always crash if we get an Exception back that is unhandled. (Rather than making it optional.)