Improved last page calculation.

Improved last page calculation when page size is changed on last page.
e.g. Suppose there are total 12 records and page size is set to 5 records/page. Go to last page, which should be 3, change page size to 10. Page#2 should be selected and it should show 2 records on it.
Merge pull request #14 from msakhawat/master

Improved last page calculation.