set documentation/make.py default to html if no format given.
commented out show in reduceChords.py
interval: descending augmented unisons are now automatically converted to descending diminished unisons; same for vice-versa with ascending diminished unisons
interval: fixed problems with interval.subtract() for augmented and diminished unisons
lily/translate: autobeam off is only set if haveBeamsBeenMade is True
smaller changes to meter, roman, stream, chords. 

git-svn-id: http://music21.googlecode.com/svn/trunk@3497 5c16147e-a200-11de-b0cc-ab0ad15e60d0