Fixed phone_to helper's string interpolation.
Collapsibles now use Twitter Bootstrap glyphicons and HTML5 attributes.
Progressively enhanced carpooling views with JS.

- Fields with errors are now properly highlighted, matching the
HTML-only behaviour.
- Unnecessary columns are hidden in HTML-only, but visible in HTML+JS.
- Cars' details are now collapsed using JS.
- Notice div now has margin-top for nicer layout.
- Removed unnecessary IDs in transports.*.html.erb.