def respond_with_local_file( source, request, date=JQUERY_VERSION_DATE )
      response = Rack::Response.new
      # for caching
      response.headers.merge! caching_headers( source, date)

      # There's no need to test if the IF_MODIFIED_SINCE against the release date because the header will only be passed if the file was previously accessed by the requester, and the file is never updated. If it is updated then it is accessed by a different path.
      if request.env['HTTP_IF_MODIFIED_SINCE']
        response.status = 304
      else
        response.status = 200
        response.write JQUERY_FILES_DIR.join(source).realpath.read
      end
      response
    end
def respond_with_local_file( source, request, date=JQUERY_VERSION_DATE )
      response = Rack::Response.new
      # for caching
      response.headers.merge! caching_headers( source, date)

      # There's no need to test if the IF_MODIFIED_SINCE against the release date because the header will only be passed if the file was previously accessed by the requester, and the file is never updated. If it is updated then it is accessed by a different path.
      if request.env['HTTP_IF_MODIFIED_SINCE']
        response.status = 304
      else
        response.status = 200
        response.write JQUERY_FILES_DIR.join(source).realpath.read
      end
      response
    end
@param [#call] app
 @param [Hash] options
 @option options [String] :http_path If you wish the jQuery fallback route to be "/js/jquery-1.9.1.min.js" (or whichever version this is at) then do nothing, that's the default. If you want the path to be "/assets/javascripts/jquery-1.9.1.min.js" then pass in `:http_path => "/assets/javascripts".
 @option options [Symbol] :organisation see {Rack::JQuery.cdn}
 @option options [TrueClass] :raise If one of the CDNs does not support then raise an error if it is chosen. Defaults to false.
 @example
   # The default:
   use Rack::JQuery

   # With a different route to the fallback:
   use Rack::JQuery, :http_path => "/assets/js"

   # With a default organisation:
   use Rack::JQuery, :organisation => :cloudflare

   # Raise if CDN does not support this version of the jQuery library.
   use Rack::JQuery, :raise => true

   use Rack::JQuery, :source_map => :true