CalChart Meeting Jan 21 2018: Play MIDI files

[kmdurand]

In order to remove the manual work from viewpsheets that has caused them to fall out of use, we'll want to import MIDI files to generate beats files. Since our beats files will be generated with MIDI, it would be best to use those same MIDI files for audio playback on the viewer (as opposed to generating a raw audio file, like OGG, from the MIDI, because the conversion opens the opportunity for time-drift between the two files)