last version to support python 3.8; small fixes and new option (--vis…

…its-limit)

fix sounds not playing on windows

truncate silence in piano sounds, fix .env mischeck

remove python 3.6 and 3.7 support, simplify requirements.txt and remo…

…ve unused try import blocks

pip installable, better badge checking, remove support for windows 7/…

…8/8.1 and macos 10.13