Add support for DRF-style pagination

When the list is paginated (paginate_by = N), the pagination data will
be added to the meta section:

{
    "data": [{
        "name": "some paginated data",
    }],
    "meta": {
        "pagination": {
            "data": {
                "count": 1,
                "next": "http://example.com/data?page=2",
                "previous": null,
            }
        }
    }
}

This is keyed so that future code can include other, not pagination
data, and so it would be possible to paginate related links using keys
similar to the "links" section.
Merge pull request #16 from jwhitlock/add_pagination

Add support for DRF-style pagination