Snakebin app tutorial, parts 1 and 2

Part 3 still needs to be implemented. That's coming soon.
The `contents` needs escaping here.

An alternative (which may be nicer) would be to have a static HTML page that invokes this script with an AJAX GET call -- the same way as you invoke it on the command line. The page would then just insert the code into the page with `$('#code').text(code_from_get)`.