nsqd: Expose Client TLS Connection Info

There isn't any introspection into client TLS [connection information](http://golang.org/pkg/crypto/tls/#Conn.ConnectionState) (what ciphers are being used, etc). I'd love to get that exposed in the status api, and through nsqadmin.


the struct tags aren't used here, they were only for reference since they match what is actually json parsed. (this is handled through simple-json not a straight unmarshal).

tls didn't have one since it just moved down a few lines.

I'm ok adding a tag for that, leaving as is, or killing the other tags.