Refactored visual feedback

Improved visual feedback - initial flash to indicate an action has taken place, followed by a progress bar type effect to show something is in the process of happening. The progress bar moves to 100% once the AJAX request has completed.

I've had to add in an extra JavaScript file to do this - wondering if there's a better way of doing things but I don't know enough about Chrome Extensions!

... Home time now :full_moon_with_face: