Use only HTTP ports for checking if services are running; use /ping endpoint.

Use only HTTP ports for checking if services are running; use /ping endpoint.

@bschwartz What do you think of this? It is basically our solution #1 from email last night.
Might be worth making a method like this:

```ruby
def all_services
  (nsqlookupd + nsqd + [nsqadmin]).compact
end
```

Then you can simplify this to:

```Ruby
def service_http_ports
  all_services.map(&:http_port)
end
```

Or potentially just remove this method since it's so simple :)