disable zoom plugin while in overview mode

plugin/zoom-js/zoom.js

@@ -1,11 +1,16 @@
 // Custom reveal.js integration
 (function(){
-	document.querySelector( '.reveal' ).addEventListener( 'click', function( event ) {
-		if( event.altKey ) {
+	var isEnabled = true;
+
+	document.querySelector( '.reveal' ).addEventListener( 'mousedown', function( event ) {
+		if( event.altKey && isEnabled ) {
 			event.preventDefault();
 			zoom.to({ element: event.target, pan: false });
 		}
 	} );
+
+	Reveal.addEventListener( 'overviewshown', function() { isEnabled = false; } );
+	Reveal.addEventListener( 'overviewhidden', function() { isEnabled = true; } );
 })();
 
 /*!