This solves #85 in a similar fashion as the color amount detection: the
cursor module now provides a trait that adds a `cursor_pos()` method to
an instance of `Write`. It also corrects that previous implementation
somewhat by making the `CONTROL_SEQUENCE_TIMEOUT` a member of the raw
module and implementing `DetectColors` for any instance of `Write`
rather than just `RawTerminal` (`MouseTerminal` for instance works as
well).