Use the new hosting service paginators for get_remote_repositories.

get_remote_repositories is now designed to support pagination, making
use of the new paginator classes. When calling get_remote_repositories,
the caller will get back an APIPaginator subclass that can be used to
paginate through all results.

The function also now takes a starting page for the pagination, and a
requested number of results per page.

This will make it easier to write web API that interfaces with
get_remote_repositories, allowing pagination to occur as expected by
callers.

Right now, only GitHub supports this function, so it's the only one that
is affected.

Reviewed at https://reviews.reviewboard.org/r/5886/