Use localhost otherwise it will not work if localhost resolves to ::1 (I...

...Pv6)

On my mac the `localhost` resolves to `::1` which leads to problem in communication problem if one side tries to connect to `lacalhost` and the other side to `::1`. The best solution is if all parties use localhost for there communication.

See also: https://github.com/rspec/rspec-core/pull/1018