Highlight and un-highlight tiles as they are selected and unselected with the click...

Highlight and un-highlight tiles as they are selected and unselected with the click and drag selection box

	  This code works but could stand a once through
	  to check for redundancies, dead code, and/or places
	  for optimization. Rendering slows down dramatically
	  as the selection box gets bigger and more tiles are
	  selected.