Fixes Bug 1036824 - Track Google Analytics Event when uses completes low-bar CTA

The thing is, this form is going to POST whether the ajax call succeeds or fails. It's just whether it does it in the background or follows the 302. Basically the difference is a UX one. (if you look at the `error` function, you'll see that it adds a dummy form and fires a `submit` event on that form)