initial support for bumpers and wheel drop sensors

- bumper example
- implement debump
- rework Roomba to have time_remaining rather than plain ol sleeps so that
  we can continuiously poll sensor data.
- configurable reset on bump/drop via attributes
- don't go through robot to send devices commands
- raise max-speed to 300mm/s
- roomba device read support
- misc roomba device commands and todos