Fixes #3: Really fix scrolling for infoboxes

Changes made:
- Switched tabbing over to 2 spaces for consistency with rest of file.
- Remove bottom and instead set height bound with max-height. We use a calc* expression (degrades to plain percentage on especially old browsers) to subtract out the margins around the info box and other UI.

*Supported reasonably now across browsers: http://caniuse.com/#feat=calc

Test plan:
- Tested on Firefox 34.0a2 and Safari 7.0.6 and infobox is correct height in both.