message: add hw v3.4, check DRV fault
diff: * Support for C++
  * Demo scripts for getting started with commanding ODrive from python
  * Protection from user setting current_lim higher than is measurable
  +* Current sense shunt values for HW v3.4
  +* Check DRV chip fault line
  ### Changed
  * Shunt resistance values for v3.3 and earlier to include extra resistance of PCB
  +* Default HW revision to v3.4
  * Refactoring of control code:
  * Lifted top layer of low_level.c into Axis.cpp
  