Release 0.4.

Mostly bugfix release, but also includes a few new features, general cleanup and robustness improvements.

- Perform clipping on overflow.
- Add very basic support for recording.
- Resample audio output for use with hardware sample rate differing
from file samplerate.
- Alphabetical file listing.
- Move to RtMidi.
- Include RtAudio and RtMidi in the source instead of requiring
separate download.
- Configuration file for global config.
- Fix program listing layout.
- Support MIDI output for automated knobs and faders.
- Using autotools again.
- Packaged for Debian/Ubuntu.
- New logo.