Makes the progress bar work for file uploads!

uses the "add" callback from the fileUpload jQuery plugin to fadeIn the progress bar and reset it before each upload, and uses the "done" callback to fadeOut the progress bar when the upload is complete and the bar is at 100%.

Adds the CSS for the bar (it has a fixed position, appearing at the top of the page like YouTube does.)

Next step: CSS markup for the page at large, and then deployment.