Get all results instead of paged

[robyedlin]

It would be really handy to add a method for retrieving all results, rather than just paged. I can work on it and submit a PR if you want.

Here's an example method from lib/createsend/list.rb:

    # Gets paged active subscribers for this list.
    def active(date="", page=1, page_size=1000, order_field="email",
      order_direction="asc")
      paged_result_by_date("active", date, page, page_size, order_field,
        order_direction)
    end

I would add something below it like:

    # Gets all active subscribers for this list.
    def all_active(date="")
      all_results_by_date("active", date)
    end