v0.20.0

Commit	Message/Description
3855606	0.20.0
9be4f0e	com: rename Mock => SerialPort to make it clear what purpose this serves.
7949f3f	Track digitalPortQueue as bits
e8b9211	Allow multiple pins to be updated before writing to the board
4df3421	CI: Drop node 4
d08665e	Add Board.clearSysexResponse(commandByte).
2bc9e5e	Replace new Buffer with either Buffer.from or Buffer.alloc
f12ca34	Minor property qualifier fix + missing coverage