Refactored Selector.by_duration() to accept DurationInequality.

NOTE: Selector.longer_than() and .shorter_than() are now deprecated.
Removed Selector.longer_than() and .shorter_than().
Refactored Selector.by_length() to accept a LengthInequality.

NOTE: Selector.less_than() and .more_than() are now deprecated.
Removed Selector.less_than() and .more_than().

Use Selector.by_length() instead.
Added Markup.musicglyph() staticmethod.

NOTE: markuptools.MusicGlyph is now deprecated. Use Markup.musicglyph()
instead.
Integrated Markup functions into Pärt demo.
Removed MusicGlyph.

Use Markup.musicglyph() instead.
Merge branch 'master' of github.com:Abjad/abjad