jQuery tweaks

We've had a number of `ReferenceError: Can't find variable: $` errors on airbrake for discussion pages.

I've checked through, and although juvia includes it's own jQuery - it seems like it relinquishes the `$` variable properly, so I'm not sure why this error would be occurring.

I've toughened up the application & surveyor js files so that they won't rely on the global `$`, which might help things