Serialization back to Volpiano (and possibly GABC)

Music loaded using chant21 contains details (word and syllable boundaries) which get lost when serializing back to Volpiano using music21.volpiano.fromStream(). It would be useful to have a custom serialization method taking them in account.

Is this something you would consider adding to chant21 - e.g. by accepting a pull request - or do you consider it out of the library's scope?