Don't (implicitly) set an initial_value in PWMOutputDevice's init method via the super() call
Don't (implicitly) set an initial_value in PWMOutputDevice's init method via the super() call

fixes #326
RPi-Distro/python-gpiozero,MrHarcombe/python-gpiozero,waveform80/gpio-zero,lurch/python-gpiozero