remove $.ready, clean up tautological p#message, move ajaxCache out of way so it can be ignored

- rather than using jQuery.ready, put script tags before closing body. this is more efficient and doesn't burden students with detail they don't need
- p#message should be identical to #message as it's an ID
- ajaxCache can be removed - POST requests [are not cached](http://api.jquery.com/jQuery.post/)