A class that encapsulates a full, well-formed MIDI file object.
This is a container object that contains a _header (:class:MIDIHeader),
one or more _tracks (class:MIDITrack), and the data associated with a
proper and well-formed MIDI file.
TICKSPERQUARTERNOTE is the number of "ticks" (time measurement in the MIDI file) that
corresponds to one quarter note. This number is somewhat arbitrary, but should
be chosen to provide adequate temporal resolution.