v1.4.0

- Feature: Adding TX FSK support.
- Feature: optional auto-quit if a certain number of PULL_ACK is missed.
- Feature: upstream and downstream ping time is displayed on console.
- Bugfix: some beacons were missed at high beaconing frequency.
- Bugfix: critical snprintf error caused a crash for long payloads.
- FSK bitrate now appears in the upstream JSON.