Completion model; Tasks and Users domain logic; Task#current #complete
	Many various changes with this update.
	- wrestled with the domain logic of tasks (how to calculate penalties? etc.)
		for a while, settled on solutions
	- prepared the #current and #complete actions. #complete uses AJAX,
		so I set up some AJAX helpers to handle errors and authentication problems
		during ajax requests.
	- Assume that most of these updates don't have adequate specs written.
		I'm going to attempt to fill in all specs tomorrow, and get the app to a
		fully tested and fully stable state.
	- It works! I could begin using it tomorrow!