[AC-2061] [iOS] Facebook logout

   // this sets the background color of the master UIView (when there are no windows/tab groups on it)
   Titanium.UI.setBackgroundColor('#000');
   
   var win1 = Titanium.UI.createWindow({  
       title:'Tab 1',
       backgroundColor:'#fff'
   });
   
   var button = Ti.UI.createButton({
   	title: 'logout'
   });
   button.addEventListener('click', function(){
   	Ti.Facebook.logout();
   })
   
   win1.add(button);
   
   var button2 = Ti.UI.createButton({
   	title: 'login',
   	top: 90,
   });
   button2.addEventListener('click', function(){
   	Ti.Facebook.authorize();
   })
   
   win1.add(button2);
   
   win1.open();
   
   
   Ti.Facebook.appid = '495338853813822';
   Titanium.Facebook.permissions = ['publish_stream'];
   Ti.Facebook.forceDialogAuth = true;
   
   Ti.Facebook.addEventListener('login', function(e) {
       if (e.success) {
           alert('Logged In');
       } else if (e.error) {
           alert(e.error);
       } else if (e.cancelled) {
           alert("Canceled");
       }
   });
   
   Ti.Facebook.addEventListener('logout', function(e) {
       alert('Logged out');
   });