Adding support for id3 TPUB and ogg/flac PUBLISHER. These tags reference the
record label that published the album/recording.

ID3 v2 -> http://id3.org/id3v2.3.0
Vorbis -> https://xiph.org/vorbis/doc/v-comment.html and http://age.hobba.nl/audio/mirroredpages/ogg-tagging.html . Note that there is discrepency with regards
to the Vorbis container. Original specs state ORGANIZATION is the noted tag, but
it seems the community has standardized on PUBLISHER (which has been used here).
updating flac and ogg tests to capture Publisher()
reverting import path for taggo example script.
Merge branch 'publisher-tag' of github:jesseward/taggolib into jesseward-publisher-tag
flac: fix typo in Publisher comment
flac_test: fix method call in Publisher() test
oggvorbis_test: fix typo in test
mp3_test: add test for blank Publisher