include references to previous/current sldie DOM elements in slidechange event

index.html

@@ -279,7 +279,7 @@ linkify( 'a' );
 
 			// Fires each time a new slide is activated
 			Reveal.addEventListener( 'slidechanged', function( event ) {
-				// event.indexh & event.indexv
+				// event.previousSlide, event.currentSlide, event.indexh, event.indexv
 			} );
 
 			Reveal.initialize({