Wrong definition of onsets

[nichtich]

The definition and implementation of RhythmPattern.onsets looks wrong to me:

1. the function does not take onsets but durations
2. it has an off-by-one error: adding duration 1 to a rhythm should add one pulse instead of a pause plus a pulse. Adding duration zero should not add anything.

Current implementation:

RhythmPattern.onsets(1, 2, 2, 1); // => [1, 0, 1, 0, 0, 1, 0, 0, 1, 0]

I recommend to add function durations and change function onsets to use positions in the ryhtm:

Expected implementation:

RhythmPattern.durations(1, 2, 2, 1); // => [1, 1, 0, 1, 0, 1]
RhythmPattern.onsets(1, 3, 6, 9); // => [1, 0, 1, 0, 0, 1, 0, 0, 1, 0]