Develop tests for each hardware subsystem

[vnprak]

Write a new Issue for each subsystem, describing the tests you plan to carry out:

• [x] LEDs
• [x] Character LCD
• [ ] RFID tags/cards & reader
• [ ] Multiplexers
• [x] Buttons

See these slides for instructions on tests.

[ffund]

Added issue for testing LEDS: #6