class library: Tuning - fix stepsPerOctave

steps per octave is essentially the number of steps per octaveRatio,
which means, its size

Signed-off-by: Tim Blechmann <tim@klingt.org>
class library: Scale - add *chromatic class method

create a chromatic scale for a specific tuning

Signed-off-by: Tim Blechmann <tim@klingt.org>