Dual callbacks on pagePerSize dropdown change

Hello @AllenFang

For some weird reason I'm doing a fetch request on `onPageChange` and `sizePerPageListChange` both.

I've encountered a scenario where `sizePerPageListChange` event also triggers `onPageChange` event. This is very similar to the example [here](https://allenfang.github.io/react-bootstrap-table/example.html#pagination)(section: Pagination Hook)

Can we avoid the table doing multiple events like these?

Thanks.