support fluentd with secure_forward

[bijaya1]

currently it seems like it cannot forward messages to remote fluentd with secure_forward.

[komamitsu]

Unfortunately we don't have a plan for TLS/SSL in this project.

You might be interested in https://github.com/komamitsu/fluency#send-requests-over-ssltls. It's another Fluentd logger supporting TLS/SSL for https://docs.fluentd.org/v1.0/articles/in_forward#how-to-enable-tls-encryption