Add Travis build-status badge in docs
Documentation / beauty pass
Add ID3v2 tag TXXX frame test
Rename T???-descr.text -> T???-descr.value
Refactor / beauty-pass on tests
Rename W???-descr.url -> W???-descr.value
Add ID3v2 tag W??? frame tests
Add ID3v2 tag WXXX frame test
Bump version patch number -> v0.1.12