Refresh method not working as expected

I'd suggest changing:

```
self.getRowsHeight(rows) && self.update(rows);
```

To:

```
self.getRowsHeight(rows);
self.update(rows);
```

To account for cases where row height hasn't changed but scroll position has (e.g. re-positioned manually by setting el.scrollTop).

Or at least an override argument could be passed in to disable the default short-circuit behavior.
