* Ripped out all the ReplayGain and Silan analysis from pypo, since
it's now implemented in airtime_analyzer. This fixes a bunch of
race conditions.
* Also renamed the replaygain field to replay_gain in airtime_analyzer
to match Airtime.
* Implemented Replaygain analysis for Ogg Vorbis, MP3, MP4, and FLAC
using python-rgain
* Added unit tests for ReplayGainAnalyzer
* Squashed stderr output in ReplayGainAnalyzer and CuePointAnalyzer
* Clean up