Use jquery-style wheel event

Conflicts:
	lib/matplotlib/backends/web_backend/mpl.js

Author: blink1073

lib/matplotlib/backends/web_backend/mpl.js

@@ -146,6 +146,13 @@ mpl.figure.prototype._init_canvas = function() {
     rubberband.mouseenter('figure_enter', mouse_event_fn);
     rubberband.mouseleave('figure_leave', mouse_event_fn);
 
+    canvas_div.on("wheel mousewheel", function (event) {
+        event = event.originalEvent;
+        event['data'] = 'scroll'
+        event.step = event.deltaY / 3.
+        mouse_event_fn(event);
+    });
+
     canvas_div.append(canvas);
     canvas_div.append(rubberband);