clean dom tree after closing popup

If i want to create popup on the fly

``` javascript
var popup = $("<div/>", {text: "my text"}).popup().popup("open");
```

its completly impossible to clean dom tree after it was closed

because destroy method in popupafterclose event will ause endless loop

``` javascript
popup.on("popupafterclose", function () {
$(this).popup("destroy"); 
});
```
