fix(timeline): Fix #2597 Zoom while dragging (#2645)

* Fix redraw order
* Fix error when option is not defined
* Allow template labels
* Add .travis.yml file
* Add experiment travis code
* Fix react example
* Fix mousewheel while dragging item bug
* Return removed lines

lib/timeline/component/ItemSet.js

@@ -259,6 +259,8 @@ ItemSet.prototype._create = function(){
   // right-click on timeline 
   this.body.dom.centerContainer.addEventListener('contextmenu', this._onDragEnd.bind(this));
 
+  this.body.dom.centerContainer.addEventListener('mousewheel', this._onMouseWheel.bind(this));
+
   // attach to the DOM
   this.show();
 };
@@ -1953,6 +1955,16 @@ ItemSet.prototype._onMouseMove = function (event) {
   }
 };
 
+/**
+ * Handle mousewheel
+ * @param event
+ * @private
+ */
+ItemSet.prototype._onMouseWheel = function(event) {
+  if (this.touchParams.itemIsDragging) {
+    this._onDragEnd(event);
+  }
+}
 
 /**
  * Handle updates of an item on double tap