The `serverOptions.host` option is ignored if `serverOptions.port` is 0 or omitted

[arikw]

When I create a tunnel with the following serverOptions, the host part is ignored:

serverOptions = {
  host: '127.0.0.1',
  port: 0
}

A bypass:

serverOptions = {
  host: '127.0.0.1',
  path: 'literally whatever', // <--- this line makes the `host` property work
  port: 0
}

See #124