Add X-Requested-By header for graylog 2.5+
Add X-Requested-By header for graylog 2.5+

Graylog 2.5+ needs this header for CSRF protection, as per http://docs.graylog.org/en/2.5/pages/configuration/rest_api.html
A CSPRNG is used, even though it is not strictly necessary, as graylog doesn't (at this time) check for replays

sensu-plugins/sensu-plugins-graylog,sensu-plugins/sensu-plugins-graylog