Converter21

There is a new MEI importer in this release, as well as many improvements to Humdrum import/export.

Remove code that treats 'Q' as equivalent to 'q' in Humdrum files.

Support Humdrum parsing and writing of RepeatBrackets (e.g. first and second endings). A few unrelated bug fixes.

The build process messed up the un-capitalization of the various package/filenames. This is the same as v1.3, but with the capitalization correct.

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.