Pass fetched records to paginator instance when building links

[thiagorp]

I had a problem recently that the count queries that were made by the processor (https://github.com/cerebris/jsonapi-resources/blob/master/lib/jsonapi/processor.rb#L88) were taking too long. These queries become very expensive as data grows. Because of this, my service was responding really slowly and the requests were piling up.

To solve that, I created a paginator that never returns the last key and calculates if there is a next page by checking if the amount of fetched resources is greater than or equal the page size. Like this:

if options[:fetched_records].size >= @size
  links_page_params['next'] = {
    'number' => @number + 1,
    'size' => @size
  }
end

But for that I need to know how many records were fetched, and with the current implementation I don't have this information. Without this information is impossible to create paginators that don't rely on the resource_count.

(Same as #997)