FOO the denominator to prevent negative delays
FOO the denominator to prevent negative delays

For the first chord it is possible for noteDelay to equal -1 because the
“- 1” is not wrapped in the denominator:

    0 + (0 / 6 - 1) = -1

But the intended order is:

    0 + (0 / (6 - 1)) = 0

If the AudioContext is created quickly enough its `currentTime` is 0
during the first calculation, which results in a negative start time and
throws an exception in MIDI.js.

Fixes #31.

filipeoliveira/song-of-github,ajacksified/song-of-github