Support sending MIDI messages

[oubiwann]

Depends upon:

• https://github.com/erlsci/midilib/issues/1
• https://github.com/geomyidia/midiserver/issues/10

Tasks:

• [x] Add the new midilib RC as a dep
• [x] Update/add term_to_binary encoders for nested tuples/lists
• [x] Expose MIDI-sending gen_server function
• [x] Test once Go midiserver supports these messages

[oubiwann]

Done.