Comment out a line so the HoTT book might compile

I wasn't sure whether or not it was an answer or a misplaced theorem or
what.  So I just commented it out.
Add contrib/.dir-locals.el for emacs
Fix a typo
Add a target to cover the HoTT book
Merge pull request #265 from JasonGross/add-hott-book-target

Add hott book target