Graphs: use dynamic width if possible

Gives better results when browser is smaller than default width.
drop old Gemfile
Upgrade to Foundation 5.1.1 from Bower

Note that we'll keep stylesheets/app.css in git, so people can just
clone, and don't need to install node and bower.
Customize Foundation to our liking

More horizontal space; everything a tiny bit smaller.
CSS Cleanup sweep

- Fixed some ugly hacks where we overwrote Foundation before.
- Dropped CSS we're no longer using.
Remove (duplicate) graph titles on overview page