Improve Connect getting started guide regarding Dependent Services

The getting started guide regarding dependent services is a bit lacking. If you are just going through the guide there is nothing that mentions what all services/clients need to be running for testing out upstream connections. At the very least we should mention that it is expected that you are running some "web" service that is listening on port 8080 that will connect to the upstream "socat" service using 127.0.0.1:9191. Even better would be a diagram of what all of it looks like:

"web" service -> Connect Proxy ("web") on port 9191 -> Connect Proxy ("socat") on a random port found via service discovery -> socat on port 8181.

It wasn't clear that in that scenario you needed two registered services and 2 other processes: socat on port 8181 and a second listening on port 8080.