Document how to use the python client with a self-hosted freerouting API

I am running the freerouting API in a docker container. I don't see any place for creating an API key for the container. However when I use the Python library to try and connect to my API, I get an error related to api keys:

```
# Cannot set the API key to none
client = FreeroutingClient( base_url="http://localhost:37864", version="dev",api_key=None)

# ValueError: API key must be provided

# Cannot not specify the API key
client = FreeroutingClient( base_url="http://localhost:37864", version="dev")

# TypeError: FreeroutingClient.__init__() missing 1 required positional argument: 'api_key'
```

As a sanity check as well, I am definitely running the API at that port:
```
$ curl http://localhost:37864/v1/system/status
{
"status": "OK",
"cpu_load": 2.3054999620327306,
"ram_used": 18,
"ram_available": 35,
"storage_available": -411,
"session_count": 0
}%
```