* Move units into API docs instead because suffixes make user code verbose and hard to read
* Rename trackWidth to trackwidth
* Make ultrasonic classes use meters instead of a mix of m, cm, mm, ft,
and inches
The main restriction is there must be an event loop running on the main thread.
No special action is required for GUI applications, but for non-GUI applications, a
RunOsxRunLoop() function is provided that needs to be called from the main thread.