Convert main.js to CoffeeScript
Created by: rspeicher
Does a bit of refactoring along the way, removing methods that are no longer required or used, and fixes a misspelling of "empty" in a function name.
Also adds two jQuery extension functions: enable and disable which
removes some duplication we were doing with disabling form fields and
adding the 'disabled' class to them at the same time. The two methods do
what you'd expect.