added exercise to chapter 3
added reference to old exercise in chapter 3
Minor tweaks to allow cleveref's poorman .sed files to work better

We'll still need to patch them to deal with autoref vs cref, but at
least we won't error or have missing braces.

The poorman option to cleveref was the only way I've found to get
htlatex to compile the book.
Merge pull request #662 from JasonGross/allow-poorman-cleveref

Minor tweaks to allow cleveref's poorman .sed files to work better
moved new exercise to the end
Add another \texorpdfstring
Merge pull request #661 from JasonGross/fix-dvi-mode

Tweaks to allow latex (and not only pdflatex) to compile the book
Merge pull request #660 from nicolaikraus/master

added exercise to chapter 3
fix typo in theorem 7.7.4
errata for cd8a902
Merge pull request #663 from JasonGross/texorpdfstring

Add another \texorpdfstring
Merge pull request #665 from mikeshulman/theorem7.7.4

fix typo in theorem 7.7.4
Mark Errata (auto)
Replace `\autoref` with `\cref` throughout.
WIP htlatex
Add a terrible hack to remove dead pictures
Make hack less terrible
Fix links in hacked page
Remove now useless duplication of replacements