fixed invalid HTML

Capybara complained: "ignoring attempt to close div with a"
removed JSON polyfill

the immediate concern is Capybara not being able to handle the
dynamically injected SCRIPT tag, thus moaning (quite verbosely) all over
the place and spamming test output

more generally though, it seems time to drop legacy support

note that this means IE7 is no longer supported, according to
http://caniuse.com/#search=json (heads-up, @mrreynolds & @tillsc)