matplotlib Code

Fix typo in a formula.

- Fixes to main book so it compiles to PDF directly from LyX, without having
to use the kludgy lyxport script at all.

- Update some of the examples with minor fixes.

- Add new workbook directory. For now, I added the .tex files as well,
though they are generated from LyX, so John can use the system without LyX
while I'm gone. Once I'm back, we can decide how to best do this in the
long run.