Write SoX playback handler

This should:

• solve audio problems:
  • fix #63 (hopefully)
  • sound problems on legacy kernel Orange Pi (@renekliment confirms)
  • CHIP with internal sound card (maybe, who knows)
• enable us to support OpenWRT
• save space and maybe (just maybe) be a little faster

The current VLC handler isn’t great and the whole thing needs a refactor regarding .stop() and resuming radio playback and stuff (#117), but that doesn’t block this. Also some methods could be reused, so it might not be a bad idea to move them to the base handler, but we’ll see how that turns out. Namely queued_play, blocking_play and process_queue.

@illperipherals showed interest in doing this, but it is currently free to take.

Random links: https://github.com/rabitt/pysox

[enclarify]

I have this feature mostly working. I need to cleanup the code and add the sox packages to all platforms this weekend and then will submit a PR for review

[renekliment]

Fixed by #140.