Add scroll event handling to javascript

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

Author: blink1073

lib/matplotlib/backends/web_backend/mpl.js

@@ -414,6 +414,7 @@ mpl.findpos = function(e) {
 };
 
 mpl.figure.prototype.mouse_event = function(event, name) {
+
     var canvas_pos = mpl.findpos(event)
 
     if (name === 'button_press')
@@ -425,7 +426,10 @@ mpl.figure.prototype.mouse_event = function(event, name) {
     var x = canvas_pos.x;
     var y = canvas_pos.y;
 
-    this.send_message(name, {x: x, y: y, button: event.button});
+    console.log(name);
+
+    this.send_message(name, {x: x, y: y, button: event.button,
+                             step: event.step});
 
     /* This prevents the web browser from automatically changing to
      * the text insertion cursor when the button is pressed.  We want