Don't fire ajax:send if ajax:beforeSend was cancelled. Don't disable form elements until ajax:send.

[MoonScript]

• Don't fire the ajax:send event if an ajax:beforeSend event-handler cancels the AJAX request (via return false). Currently, it's lying to us because you would still see an ajax:send event even if no request was made. This will make it honest by only firing ajax:send if a request was actually heading to the server.
• Don't disable form elements until the ajax:send event fires. Currently, it disables form elements when the ajax:beforeSend event bubbles up to the document. So if you had your own document-level ajax:beforeSend event-handler that was bound after the one from jquery_ujs.js, your form elements would still get disabled, even if you cancelled the AJAX request by doing return false from your event-handler. This will wait to disable the form elements until we're sure that an AJAX request is actually being made, by hooking into the ajax:send event.

[MoonScript]

Thanks @lucasmazza. Do you think you could also merge in 336? It's been out there for a while!