def html?(status, headers)
      !Rack::Utils::STATUS_WITH_NO_ENTITY_BODY.include?(status.to_i) &&
        headers.key?('Content-Type') &&
        headers['Content-Type'].include?('text/html')
    end
def html?(status, headers)
      !Rack::Utils::STATUS_WITH_NO_ENTITY_BODY.include?(status.to_i) &&
        headers.key?('Content-Type') &&
        headers['Content-Type'].include?('text/html')
    end
Taken from:
 https://github.com/rack/rack-contrib/blob/master/lib/rack/contrib/jsonp.rb