Resolving build errors.

[bsb808]

Hey Allen!

I'm teaching a MATLAB class starting next month and am planning to use your book as a baseline. When I tried to build PDF locally I ran into a couple errors, which I believe this PR may resolve:

1. Appears that the titlepages.tex file may not have been added to the repo. I attempted to recreate it based on what had been removed from main.tex. There appear to be some differences in the resulting PDF and your release. I suspect that is because of an incomplete restoration of the titlepages.tex file.
2. Small error with an underscore that was breaking my build.

If you are still tracking this project would it would be great to keep my fork synch'd the original.

All the best, Brian