DO NOT PACKAGE - RELEASE CANDIDATE VERSION, WAITING FOR TRANSLATORS

Full 0.3.0 release is slated to release next Saturday (earlier if all translations arrive before then), cc translators: @phaerrax @flipflop97 @rene-coty @sheeepdev @sabriunal @igor-dyatlov

This is a fairly large release, and includes quite a few changes, both under the hood and more user-facing:

• Added additional tag fields (#30) - allows for setting more nonstandard tags.
  
• Greatly improved performance and squashed some memory leaks. Loading files is noticeably faster now, and so is switching between files.
  
• Added cover art support for m4a and ALAC files, as well as WAV and WMA. This was done as part of the migration from multiple different tagging libraries to only Mutagen.
  
• And added many more bugfixes and improvements - see the 0.3.0 milestone for a full list.
  

For package maintainers: you can drop the dependency on pytaglib and eyed3. Mutagen is now required.