Add details about flashing Varmint with firmware

[bsutherland333]

Instructions on how to wire up a debugging harness for developing with the Varmint as well as how to flash a release version of the firmware with DFU is needed.

[JMoore5353]

Documentation on flashing Varmint with firmware has been done, but we still need to create instructions on how to wire up the debugger harness for the Varmint.

[JMoore5353]

@iandareid do you have the instructions for wiring up the debugger harness for the Varmint?