Added support for drawing rectangles during playback (somewhat)

There are some issues still:
	(1) The playback replays all of the rectangles and does not clear those that are simply resizes of previous rectangles. This will need to be recoded in writing.js
	(2) The rectangles are filled in. Simply set each rectangle style to fill:none within the slides.rb processing script.

TODO:	Clear full screen
	Draw circles
	Draw lines in larger sections (with many subsections)
	Change Slides
	Start moving cursor
	More rigid code for playback with issues getting the svgs