Add empty test audio files
Rewrite mediafile tests
Extract assertTags method
Simplify MediaField descriptor
Refactor get/set into StorageStyle
Add MP3 StorageStyle class
Add serialize method for StorageStyle
Add unpack method for storage style
Refactor MP4 tag decode
Refactor StorageStyle packing
Tests include all file formats
Add UFID storage style
Test empty mediafiles
Use tempdir for mediafile tests
Refactor MP3TextStorageStyle
Include key in error message when tags do not match
Lyrics are not stored as array
Fix packaging
Remove unused id3 specific stuff
Refactor serializing