Accept 0.0 as withJitter
Accept 0.0 as withJitter

If we don't want to set the jitter factor after all, we can reset it
by setting it back to 0.0.

jhalterman/recurrent,jhalterman/recurrent,jhalterman/failsafe,failsafe-lib/failsafe,failsafe-lib/failsafe,jhalterman/failsafe