Overhaul heartbeats - Githubissues

When the latest heartbeat ack expires, immediately start sending disabled heartbeats instead of just canceling the heartbeats
Fixes heartbeats never resuming after a heartbeat ack timeout
Don't start heartbeats while the heartbeat ack timeout is expired
- If the application attempts to do this, the heartbeat will not be started until after the next heartbeat ack is received.
Check for expired heartbeat acks every 250ms instead of 1000ms
Use steady_clock instead of system_clock
Increase the SPARK heartbeat period from 10ms to 20ms (same as the REV common heartbeat)

REVrobotics / node-can-bridge