Portaudio / Mpg123 Integration

This changeset replaces the Coreaudio layer with Portaudio for hardware
abstraction and libmp123 for decoding.

Extracts audio player as gem named audite.

```
brew install portaudio
brew install mpg123
bundle install
```

```
[DownloadThread] -> [mp3] -> [mpg123] -> [PlayerProcess] -> [portaudio]
```