added id to object which called the menu

Hi,

just added an id to make it able to figure out which object called the menu.

Usage example
```javascript
context.attach('.class', [{
				text: 'hello world',
				action: function(e){
					e.preventDefault();
					var callerId = $(this).closest('ul').attr('data-contextjs-callerid');
					var $ObjectWhichCalledTheMenu= $('[data-contextjs-id="' + callerId + '"]');
					
				}
			}]);
```