Support for completed items under findCompletedItems service

[saurori]

It would be nice to have support for searching completed items under the findCompletedItems service (http://developer.ebay.com/DevZone/finding/CallRef/findCompletedItems.html). Example:

    def find_completed_items(params)
      raise ArgumentError unless params[:keywords] or params[:categoryId]
      response = get_json_response(build_request_url('findCompletedItems', params))
      response.trim(:findItemsAdvancedResponse)

      if response.response.has_key?('searchResult') && response.response['searchResult'].has_key?('item')
        response.results = response.response['searchResult']['item']
      end
      return response
    end