Run Makefile to generate the docs.

This is a huge, kludgy approach to the problem of reusing
documentation from Racket for WeScheme, in the sense that we
essentially copy-and-paste the content.  We try to be good about it by
doing this copy-and-pasting structurally rather than textually, but
this is still not great.

Note that this expects to be run under DrRacket 5.3.2.  Some of the
processing we're doing is very sensitive to the exact English prose
used in the documentation of Racket, so if we use another version,
there are probably a few things that will need adjustment.