[racket] Volunteer for the Racket SICP package

Yes, I put a call for a new maintainer at the top of the documentation 
("http://www.neilvandyke.org/racket-sicp/").  The package could benefit 
from a paid TA/RA or super-dedicated hobbyist, making everything smooth 
for each of the book's problem sets.

There are at least two ways that you could approach it:

* Just work through SICP, and make incremental changes to the existing 
code as you encounter problems.

* Start over from scratch with everything but the Picture Language (by 
Mike Sperber's and Jens Axel Soegaard).  The reason is that Racket's 
support for defining new languages is now nicer, and much better documented.

In either case, I was thinking of eventually using the "#lang" line to 
specify which assignment or chapter you were doing, so you get exactly 
the right definitions.

Neil V.