conn: clearly require ConnDelegate
Merge pull request #53 from mreiferson/conn_delegate

non-obvious nsq.Conn requiring nsq.ConnDelegate
per-connection TLS config and set ServerName
Merge pull request #54 from jehiah/tls_configs_54

Improve TLS support
refactor config struct tag handling
Merge pull request #55 from jehiah/config_handlers_55

refactor config handling