Fixes bug with Teensy 2.0 that required a power cycle after device reset

Refactor and add support for Teensy 2

Update to work with megaavr devices

Add Teensy 4 library and tripped() method

Add support for Teensy 4

Reformatted for Arduino IDE 1.5 library specifications.

Added enabled method.

Generalized to work with both AVR and Teensy boards.

Updated to Arduino 1.5.x+ library specification