Pkgcloud integration

This sets up some initial pkgcloud integration to shunt the images off to a CDN.
Wait, so, clear up my misconceptions about JavaScript here.

```
  var cdnUrl;

  // Won't cdnUrl be undefined here no matter what from the local declaration above?
  if (cdnUrl) {
    req.cdnUrl = cdnUrl;
    next();
    return;
  }
```