Update jquery.aSimpleTour.js

Added callbacks:

 * endCallback
 * tooltipCallback

Exemple:

$.aSimpleTour({
          data : [
            { 
              element: '#MyID', 
              tooltip : 'This is a tooltip for some element #MyID',
              position : 'TR',
              text : '<p>Some Text</p>',
              tooltipCallback : function(){ alert('CALLBACK'); }
            },
            { 
              element: '#MyID2', 
              tooltip : 'The last link of some ul list',
              position : 'TR'
            }
          ],
          controlsPosition : 'TR',
          welcomeMessage : 'Yeah Bro',
          endCallback: function(){ alert('coucou, its ended'); }
        }
        
        );