tls support

[juliangruber]

when -tls-required

[juliangruber]

from go-nsq:

    // To set TLS config, use the following options:
    //
    // tls_v1 - Bool enable TLS negotiation
    // tls_root_ca_file - String path to file containing root CA
    // tls_insecure_skip_verify - Bool indicates whether this client should verify server certificates
    // tls_cert - String path to file containing public key for certificate
    // tls_key - String path to file containing private key for certificate
    // tls_min_version - String indicating the minimum version of tls acceptable ('ssl3.0', 'tls1.0', 'tls1.1', 'tls1.2')
    //
    TlsV1     bool        `opt:"tls_v1"`
    TlsConfig *tls.Config `opt:"tls_config"`