Music21 v.2.0.8 (beta) released

The newest release of the music21 v.2 (beta) developments improves the stability and performance of the system. 

The biggest change in this version is the movement of all experimental modules into a new "alpha" sub-package; in the future, all releases that add something useful to music21 but which are not well tested or mostly documented will begin in this folder. They may graduate into the main music21 mainspace at some later point, remain in "alpha", or be removed. Among the modules that are moved include: webapps (system for running music21 as a WSGI service-oriented architecture), trecento (fourteenth-century musical analysis), theoryAnalysis(common-practice error detection), counterpoint/species (first-species counterpoint generator), medren (miscellaneous pre-1600 applications; this will return soon after refactoring), contour(contour analysis), chant (Gregorian chant generation), and analysis.search (find scales inside Streams).

The "demos" directory has also been reorganized. The next release will focus on making this directory easier to use.

Bug fixes and improvements:

• search.lyrics -- modules for searching within lyrics while retaining position information about matches.
• Interval objects have been improved to have additional properties.
• .priority changes will automatically re-sort Streams. This change will make .priority more useful.
• Stream.elementsChanged() is a new method that can trigger a cache clear for Streams.
• Stream.remove() gets a recurse function.
• Lilypond color works again (thanks Ringw)
• Accidental becomes a SlottedObject -- pro: much faster. con: arbitrary attributes cannot be added to Accidentals.
• MuseScore 2 is now discovered automatically in python3 configure.py.
• Tremolo support (including in MusicXML)
• Unlikely bugs in Chord fixed.
• MIDI support for > 16 channels output.
• Fixes for PIL/Pillow support of more versions
• More places taking advantage of exact fractions in music21 offsets and lengths which used to be kludges