Issue with `json` output

```
from nglui import statebuilder as sb

root_id = 864691136137805181

state_dict = sb.make_neuron_neuroglancer_link(client, root_id, return_as="json")
```

gives 

```TypeError: ChainedStateBuilder.render_state() got an unexpected keyword argument 'ngl_url'```

the same thing runs without changing `return_as`