New MEI parser

Use a new MEI parser from converter21. Compare grace notes (including whether they are accented or unaccented). General bug fixes.

Comparison of arpeggios and multiple endings

Add support for comparison of ArpeggioMark, ArpeggioMarkSpanner, and RepeatBracket.

Use converter21's Humdrum parser

v1.3.0

Depend on (and install during setup) converter21.

Add lyrics support

Add support for comparison of lyrics within AllObjects (default diff) and AllObjectsWithStyle.

Diff non-notes, and optional detailed diff

Added diff of non-notes (clefs, etc), as well as detailed diff including style (text fonts, stem direction, note color, etc).
New DetailLevel parameter: GeneralNotesOnly (like v1), AllObjects (default), AllObjectsWithStyle (notice detailed differences)

Release version 1.0.1

Initial public release.