Change midi-key-player to only play notes that aren't already playing
Change midi-key-player to optionally filter out irrelevant devices
Update speclj dependency to 3.0.0
Refactor midi-player out of midi-key-player and buf-player
buf-player -> midi-buf-player
Rename midi-key-player's player key: :key-player -> :midi-key-player
Add midi-perc-player for playing different insts based on the played note
Support filtering out irrelevant channels for midi players