Fix reserved word parsing errors in IE < 9

`in` and `with` are reserved words, they need to be strings when used as keys in
and object literal.
Bump to version 2
Rename declare_messages as uses_messages

Also includes a few improvements. messages_to_lookup is now a set, so we don't
send duplicates to the browser. The #uses_messages method can be called more
than once if the user wishes.
Reinstate an Html module

So, I removed the old HTML module earlier in this v2 drive because I kind of
hated it. It seemed gratuitious. But I later realised I needed to keep a cleanish
interface like this in order to support the extension gems. So it's back. Sort
of. I've renamed the module to a) match the Formtastic module and b) stop fighting
Ruby's camel case expectations. So the extension gems will still need an upgrade.
Add json Accept header to judge.get

Because I should have done this already.