Closing bug involving heartbeat timeout.

[fulmicoton]

The timeout logic was inverted. A timeout is when now > deadline.

Closes #48.

Checklist

• [x] tests are passing with cargo test.
• [ ] tests and/or benchmarks are included
• [ ] documentation is changed or added
• [x] commit message is clear

[o0Ignition0o]

The failed checks seem to be gh / networkign related, merging this!