Stop successive edges from linking up

I'm trying this library out, and I have to admit that it is very useful.

One issue that I'm having right now is that drawing two independent edges ends up with a third edge being drawn. Simple example:

```
graph = G.graph({
antialias: true,
bgColor: "black",
edgeWidth: 1,
nodeSize: 10
});
G.node([0, 0, 0], {id: 0}).addTo(graph);
G.node([0, 1, 0], {id: 1}).addTo(graph);
G.node([1, 0, 0], {id: 2}).addTo(graph);
G.node([1, 1, 0], {id: 3}).addTo(graph);

G.edge([0, 1]).addTo(graph);
G.edge([2, 3]).addTo(graph);

graph.renderIn('frame');
```

Expected result:

```
O O
| |
| |
| |
| |
O O
```

Result with the current version of graphosaurus:

```
O O
|\ |
| \ |
| \ |
| \ |
O O
```

This is problematic for me. If I'm doing something wrong here, I can't see what it is.

I have tried looking around the code and finding where this happens, but I chose this library specifically to avoid the learning code of three.js - so I don't know where this error is creeping in.