Remove Halo.pl!

- [x] update documentation to inform how to set up systemctl to start this service at boot and configure uart
- [ ] use json instead of `000,000,000,000\n`
- [ ] tests
- [ ] fixup! commit this abomination of a PR
- [x] remove halo.pl
- [x] remove serialport from package.json, and `node_serialport.js`
- [x] refactor server to use properties instead of globals for `buffer`, etc
- [x] remove unnecessary logging or change production logging level