Add time2html

From http://ssr.msr-inria.inria.fr/hudson/job/ssr_v8.4/ws/ssr/tools/
Use generic lua version
Always make .timing files

It's cheap, and we'll use them to make html files.
Add targets for timing-html files
Add timing html as a target to travis
Make the timer work again

It doesn't like parentheses, so pipe it through a script.
Ignore generated timing files.
Install a valid lua package
Merge pull request #329 from JasonGross/coq-time

Coq timing