v3.1.0

• Fixes repeating frame functionality
  • See REVrobotics/CANBridge#24 and REVrobotics/CANBridge#25
• Overhauls heartbeat sending internals
  • See #18
  • Makes it so that a given heartbeat doesn't stop being sent once it's started
  • Improves performance and reliability of heartbeats
  • Reduces the frequency of the SPARK heartbeat to match the REV common heartbeat
  • Fixes heartbeats never resuming after a heartbeat ack timeout