Create a single fragment event per fragment-index

For backward-compatibility, add a new 'fragments' property to the
fragmentshown and fragmenthidden events. The 'fragment' property still
returns the first fragment.

js/reveal.js

@@ -1916,10 +1916,10 @@ var Reveal = (function(){
 
 				toArray( fragments ).forEach( function( element ) {
 					element.classList.add( 'visible' );
+				} );
 
 				// Notify subscribers of the change
-					dispatchEvent( 'fragmentshown', { fragment: element } );
+				dispatchEvent( 'fragmentshown', { fragment: fragments[0], fragments: fragments } );
-				} );
 
 				updateControls();
 				return true;
@@ -1950,10 +1950,10 @@ var Reveal = (function(){
 
 				toArray( fragments ).forEach( function( f ) {
 					f.classList.remove( 'visible' );
+				} );
 
 				// Notify subscribers of the change
-					dispatchEvent( 'fragmenthidden', { fragment: f } );
+				dispatchEvent( 'fragmenthidden', { fragment: fragments[0], fragments: fragments } );
-				} );
 
 				updateControls();
 				return true;