`vulcan update` fails

One of the upstream dependencies (`request`) now requires at least Node 0.8.x:

```
       npm ERR! Not compatible with your version of node/npm: request@2.16.6
       npm ERR! Required: ["node >= 0.8.0"]
       npm ERR! Actual:   {"npm":"1.1.4","node":"0.6.20"}
```