ALSA: use plug:default instead of plughw:0,0

Don't acquire hardware card, so PulseAudio and dmix may be employed to use other ALSA applications concurrently

Source: http://www.alsa-project.org/main/index.php/DeviceNames
Merge pull request #32 from aitap/alsa_plug_default

ALSA: use plug:default instead of plughw:0,0