ALSA volume widget

This widget uses amixer to get and set the current volume level and it also exports functions you can use
in keybindings to change the volume and mute / unmute your soundcard.

To set the card to use, use
    obvious.volume_alsa.setcardid(id)
in most cases the default (0) suffices

To set the channel to control, use
    obvious.volume_alsa.setchannel(c)
the default is "Master", you might need to set it to "PCM"

Use
    obvious.volume_alsa.raise()
    obvious.volume_alsa.lower()
    obvious.volume_alsa.mute()
to control the volume with keybindings.

To add this widget to your configuration, insert
    require("obvious.volume_alsa")
into the top of your rc.lua and add obvious.volume_alsa() to your wibox.

If you want to use the data gathered by this widget, you can use the function obvous.volume_alsa.get_data().
It returns nil on failure, otherwise it returns a table with the following fields:

    volume  a number representing the current volume from 0 to 100
    mute    a boolean value describing whether the channel is muted or not
