drag and drop changes
	some changes to the inheritance of classes: followable's inherit from dragable's instead of arrangeables.
	this change was made to allow them to throw zone events when being dragged over a drop zone.
	it doesn't seem to be working at this time, but this change should allow more tobii functionality later, since the tobii sprite's inherit from that class.

There is a new demo, currently non-functional, that uses this new functionality.

some stimuli folders have been renamed to keep the use of _ and - more consistent