Implement non-standard tuplet numbers

[hanwenn]

lgtm


http://codereview.appspot.com/12661/diff/1/11
File scm/output-lib.scm (right):

http://codereview.appspot.com/12661/diff/1/11#newcode307
Line 307: (define-public ((tuplet-number::append-note-wrapper function
note) grob)
rename function to describe what it does.

http://codereview.appspot.com/12661/diff/1/11#newcode322
Line 322: (define-public
((tuplet-number::non-default-tuplet-fraction-text denominator numerator)
grob)
maybe you can make these optional?

  (func arg arg1 . opt-args)

there are also std libs to make functions with keyword arguments.  Maybe
you can use those to fold some of the functions together.

http://codereview.appspot.com/12661