Rests, tuplets, chords pretty much done, bar pre/suffixes handled

Chords mostly work -- rarer scenarios such as when later notes have
longer durations not handled yet: "[a2b4]"

TODO: Handle multiple voices, handle lyrics, make grammar tolerant where
need be, & throw errors for improper formats.
Voices supported
Merge pull request #41 from hogbait/songParser-reads-songs

Rests, tuplets, chords, bar pre/suffixes, & voices