Added support for flood protection

[esamattis]

This is pretty simple implementation, but works nicely.

[martynsmith]

Cheers, the only downside I see to this is the potential 1 second delay on a send in isolation (i.e. if the queue is empty, there's a potential delay on the first send).

Seems like a small price to pay for flood protection for now though :-), and if someone cares enough they can fix it up :p