AudioKitCore::LinearRamper: support for horizontal segments
AudioKitCore::LinearRamper: support for horizontal segments

The ramper could only ramp up or down, so couldn't handle just maintaining a constant value for some interval. Now it can.

eljeff/AudioKit,audiokit/AudioKit,audiokit/AudioKit,adamnemecek/AudioKit,eljeff/AudioKit,adamnemecek/AudioKit,eljeff/AudioKit,adamnemecek/AudioKit,adamnemecek/AudioKit,audiokit/AudioKit,eljeff/AudioKit,audiokit/AudioKit