BUG: AnalogOutput

Hello there, this is amazing, thanks!


I found a bug in Observars/ObserverAnalogOutput.h: 
`
void ObserverAnalogOutput<T>::OnNext(T value)
{
    analogWrite(value);
}
`


Should be:
`
void ObserverAnalogOutput<T>::OnNext(T value)
{
  analogWrite(this->_pin, value);
}
`


Again, amazing work!