code: function(evname, callback, context) {
      this._events = this._events || {};
      var a = this._events[evname] = this._events[evname] || [];
      a.push({
        cb: callback,
        ctxt: context || this
      });
      return this;
    }
docs: Bind event listener
  
  @param {string} name of event
  @param {function} callback if event is triggered
  @param {object} context in which callback is called
  @return {this}