Working channel and volume change

[mmende]

Hey,

I have forked your code and implemented the set channel and volume features. To set the channel the single digits of a channel will be send with a short delay between them. To change the volume the volume up or down key will be send as much times as the volume parameter indicates or the mute key will be triggered when 0 will be send. If this hacky way of implementing this features is good enough for you I can submit a pull request.

Kind regards