Laid some groundwork in roman.py for parsing augmented sixth chords.


git-svn-id: http://music21.googlecode.com/svn/trunk@3519 5c16147e-a200-11de-b0cc-ab0ad15e60d0
Preparing Roman numeral figure-matching regular expressions for augmented
sixths.


git-svn-id: http://music21.googlecode.com/svn/trunk@3520 5c16147e-a200-11de-b0cc-ab0ad15e60d0
roman.RomanNumeral can now omit more than two steps.

Before, at most two steps could be omitted when parsing a Roman numeral figure.


git-svn-id: http://music21.googlecode.com/svn/trunk@3521 5c16147e-a200-11de-b0cc-ab0ad15e60d0
Streamlined alteration parsing in Roman numerals.


git-svn-id: http://music21.googlecode.com/svn/trunk@3522 5c16147e-a200-11de-b0cc-ab0ad15e60d0