Guide for clock module: http://henrysbench.capnfatz.com/henrys-bench/arduino-sensors-and-input/arduino-tiny-rtc-d1307-tutorial/
TODO:
software only:
- split default variables out to .h file
- split functions out to .h file(s)
- implement target setting for day and night from serial
- implement day and night threshold setting from serial
move to physical controls:
- implement clock setting from button
- implement target setting for both day and night from button
- implement day and night threshold setting from button
- implement temperature measuring from physical sensor