added firstItem, lastItem and a unit test for pagination

[jeff1985]

this fixes issue #6

note: i used firstItem() and lastItem() which seems to describe the functionality very good. see laravel paginator as widely used reference implementation http://laravel.com/api/5.0/Illuminate/Contracts/Pagination/Paginator.html

[onassar]

Thanks for the pr. How do I make changes? Haven't needed to before, but there are some things I'll want to update.

[jeff1985]

I suggest you accept the pull request and do the changes you like.

[onassar]

Gotcha thx