Fix a bug causing reloadData to fail for new content

Steps to reproduce the bug:
1. Present an SYPaginator with a set of images
2. Change the data source's set of images
3. Call reloadData on the paginator

**Expected:** Paginator content updates showing new image set
**Actual:** CurrentPage is removed and new content is not shown until user changes index

`_setCurrentPageIndex` rejects requests if the index has not changed and the call was made internally. 

I assume the original intention was the opposite; do nothing when the developer requests a page change to the currently shown index.