Converter21

Use float instead of Fraction where possible (i.e. where accurate) for speed. Implement arpeggio support, which will only function if you are using a version of music21 with arpeggio support (v8.0.0a9 or later). Improve metadata support if a version of music21 with improved metadata support is present (v8.0.0a9 or later).

The Humdrum importer now parses lyrics and verse labels, and the Humdrum exporter writes them out.

Improved fidelity of import/export of:
- MetronomeMark
- Fermata
- Barline/Repeat
- Cue-sized notes
- Colored notes
- Notehead shapes
- Placement (including centered placement)
- Sforzando and subito forte
- RDF
- Style
- Dynamic with surrounding text

First release.