removes flac test as it was broken on osx, adds get_audio_devices
adds Gain node with * operator
Merge branch 'master' into dev_select
refactored AudioNode to contain a AudioRenderer, tests passing
adds some design notes
fixes issue where portaudio task was killing the root mixer
fixes imprecise SinOsc
ports AudioInput to new type structure
adds WhiteNoise AudioNode
adds LinRamp node
adds ability to control SinOsc freq from a signal