title: add a tooltip to an EXTJS Button
body: <p>I am trying to add a tooltip to my button, I tried differents ways, but nothing happen when i put the mouse under the button, this is a part of my code when i tried to add this tool tip 
  this when i created the button called guestButton </p>
  
  <pre><code> {
      xtype : 'button',
      id : 'guestButton',
      text : 'Guest User',
      handleMouseEvents: true,
      width : 80,
      x : 70,
      y : 150,
      formBind : false,                       
      handler : function() {
      this.up().LoginGuest();
      }
  </code></pre>
  
  <p><strong>and here when i tried to create the tooltip</strong> </p>
  
  <pre><code>    var tooltips = [{
              target: 'guestButton',
              html: 'A very simple tooltip'
          }];
  Ext.each(tooltips, function(config) {
          Ext.create('Ext.tip.ToolTip', config);
      });  
  
  Ext.QuickTips.init();
  </code></pre>
  
  <p>Thanks ! </p>