Working stepper system with light test

Stepper system (add stepper, timer library, etc) are all written and
working, committing this halfway through addition of all 8 steppers -
still not sure if it's extensible to this case.
Trying to declare Stepper objects properly

Idea is to initialize global array of pointers, then instantiate objects
in main function, storing their pointers in the global array.
Stepper + Comms Complete

Everything is set on the stepper front; I can control all 8 stepper
channels independently over TWI. There were some issues with stepper
tick interrupt preventing TWI comms, but this was fixed by prescaling
the tick timer so that it doesn't fire as often.