v2.3.0

• support for interval direction, i.e. an 'M3' is a '-M3' if the interval is between two voices that are crossed with respect to their staff position
• inclusion of experimental qualityControl file in scripts which can be used to make sure that a file can be imported by music21 and to run a basic verification that the parts line up properly
• begin tracking experimental MedievalNoteRestIndexer script in scripts folder
• basic testing suite for DissonanceIndexer
• tons of docs improvements (thanks @maxalbert)