Add dvimode, remove pagecolor package

This closes #666.

Travis will now test dvi mode for us.  This is primarily useful for
htlatex.

Move the bmpsize hack for bounding boxes to a separate .tex file, to be
used in other files.

We also now silence the first two runs of (pdf)latex, because travis was
complaining about the log file being too big.
Retry wget resolution when downloading fails
Split the dvi and non-dvi targets
Remove latexmk dvi target

latexmk in dvi mode is too verbose for travis.  Maybe we should just
grep out most of the lines on travis?  But I'm lazy and disabling the
target is easier.
Add *.out.pdf to .gitignore
Merge pull request #670 from JasonGross/dvi

Add dvimode, remove pagecolor package
Merge branch 'master' of github.com:HoTT/book

Conflicts:
	errata.tex    .... there was an \autoref
Merge pull request #668 from andrejbauer/master

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
Make more things render as text rather than images.