[racket] Today's history lesson: Old Racket development history

I've taken all the old Racket development history from before
development moved to SVN, and converted it to git.  You can view it
all here: https://github.com/samth/old-plt

Some interesting commits:
 * The first commit: https://github.com/samth/old-plt/commit/6155845eea
 * The first commit by Matthew:
https://github.com/samth/old-plt/commit/68b3e2673
 * The introduction of the module system:
https://github.com/samth/old-plt/commit/79104357

If you notice any issues with the conversion, let me know.

Have fun exploring the history,
Sam