Simple websocket attempt, links not being rendered

I've been trying to use vivagraph to represent a tree (ideally later with dynamic updates to nodes on the tree)

The nodes get placed as I'd like, but the links don't render.

Does placing nodes change the behavior of links?

Please advise?

HTML/JS:
``` html

VivaTree


function onLoad() {
var graph = Viva.Graph.graph();
var layout = Viva.Graph.Layout.constant(graph)

var renderer = Viva.Graph.View.renderer(graph, {
layout : layout
});
renderer.run();

var ws = new WebSocket('ws://localhost:8080/');

ws.onmessage = function(event) {
console.log('Received Data: ' + event.data);
var message = JSON.parse(event.data);

if ('command' in message) {
//FIXME: Supoprt batch 'commands'
graph.beginUpdate()
switch(message['command']) {
case 'addNode':
console.log('running addnode')
graph.addNode(message['id'], message['data'])
layout.placeNode(function(node) {
return {x: message['x'],
y: message['y']};
});

break;
case 'addLink':
console.log('running addLink' + message['from'])
graph.addLink(message['from'], message['to'])
break;
default:
console.log('Unsupported command.')
}
graph.endUpdate()
}
};

}

body, html, svg { width: 100%; height: 100%; overflow: hidden; }

```

Simple Python wrapped with [websocketd](http://websocketd.com/)
```python
#!/usr/bin/env python3
from sys import stdout
import json
import math

x_spacer = 30
y_spacer = 40

# Row in tree. (top is 0)
def get_row(id):
if id == 0:
return 0
else:
return math.floor(math.log2(id+1))

def get_y_pos(id):
return y_spacer * get_row(id)

def get_x_pos(id):
if id == 0:
return 0
row = get_row(id)
shift = 2 ** row + 2 ** (row-1) - 1.5
adjust = id - shift
return x_spacer * adjust

# Count from 1 to 10 with a sleep
for count in range(0, 2 ** 4 -1 ):
output = {
'command' : 'addNode',
'id': count,
'x' : get_x_pos(count),
'y': get_y_pos(count),
}
print(json.dumps(output, sort_keys=True))
stdout.flush()

uplink = int(math.floor((count-1)/2))
if uplink >= 0:
output = {
'command' : 'addLink',
'from': count,
'to': uplink,
}
print(json.dumps(output, sort_keys=True))
stdout.flush()
```

Data being sent over socket
```
{"command": "addNode", "id": 0, "x": 0, "y": 0}
{"command": "addNode", "id": 1, "x": -15.0, "y": 40}
{"command": "addLink", "from": 1, "to": 0}
{"command": "addNode", "id": 2, "x": 15.0, "y": 40}
{"command": "addLink", "from": 2, "to": 0}
{"command": "addNode", "id": 3, "x": -45.0, "y": 80}
{"command": "addLink", "from": 3, "to": 1}
{"command": "addNode", "id": 4, "x": -15.0, "y": 80}
{"command": "addLink", "from": 4, "to": 1}
{"command": "addNode", "id": 5, "x": 15.0, "y": 80}
{"command": "addLink", "from": 5, "to": 2}
{"command": "addNode", "id": 6, "x": 45.0, "y": 80}
{"command": "addLink", "from": 6, "to": 2}
{"command": "addNode", "id": 7, "x": -105.0, "y": 120}
{"command": "addLink", "from": 7, "to": 3}
```

Start with the HTML/JS example using vivagraph.js, especially the renderer setup and the graph.addNode/graph.addLink calls inside the WebSocket message handler. Run it with the provided Python websocketd script and inspect whether the streamed links appear after their nodes; done means the tree links render for the supplied data.

Written by the indexing model from the issue text.