MIDI file reading using python-midi from Github.

Follow instructions in the README.md to install the necessary dependencies.
Currently can convert from midi file to an output including piece metadata
key signature, time signature) and list of note times/names/velocities
(how hard key was pressed). Still todo: parse tempo from metadata, represent
note output in a more useful way (eg align simultaneous notes), and test with
more complicated/realtime midi files to ensure that formatting works the same
way.
(Spent fifteen minutes trying to quit vim, to no avail, and ended up using -m instead...sorry if this is formatted incorrectly.)