Martypy

- Add streaming sound support

- Support for ground and obstacle detection using the IR/Colour foot sensors
- User callbacks on data received from the robot in the background
- Automatically re-establish the WiFi connection if Marty reboots

- Improved connection setup process (preparation for higher USB speeds)

- New functions for controlling the disco add-on lights
- New distance sensor function for Marty V2 that returns the distance in mm

- Default `movetime` parameter for the `dance()` has been changed to 3000ms instead of 4500ms

- New `Marty.add_on_query` method provides low-level access to Marty's addons
- New `Marty.is_conn_ready` method for checking if Marty is connected
- Small changes to the dictionary returned by `get_power_status()`
- Stale power, servo and other information is no longer presented if updates from Marty cease
- Various under-the-hood improvements, bugfixes and preparations for future features