Add TCP_NODELAY to TCP sockets.

Just like hiredis client:
https://github.com/redis/hiredis/blob/8332a88393cc79b6f7d431859e5bbf157d8c1ea3/net.c#L323
And the redis server itself:
https://github.com/antirez/redis/blob/0bcc7cb4bfe733e7ea12599a926e52aece3bfa50/src/networking.c#L73

I also it gives (in some minor tests I did) a minor performance benefit in some cases. I am no Unix domain socket to know if it's applicable there?