When using Python 3.3+, update dependency on pyserial-asyncio

[controlsfreek]

When cloning the sdk and running examples, python complains about invalid decorators on asyncio functions.

sdk calls for pyserial-asyncio==0.4, however 0.6 is needed with python 3.3+

Force-install 0.6 fixes the issue:
pip3 install pyserial-asyncio==0.6