Refactor the Radiator

Following up from #214 begin a refactor of the radiator so that the data is retrievable as a json document.

**Not ready for merge.** I will update radiator.js to include auto-reload of /radiator.json contents.

Minor updates: added heading Puppet Node Summary is added, and adjusted the spacing to allow four-digit node counts cleanly.

/radiator.json
```javascript
{ display: [
  { key: "unresponsive",
    name: "Unresponsive" },
  { key: "failed",
    name: "Failed" },
  { key: "pending",
    name: "Pending" },
  { key: "changed",
    name: "Changed" },
  { key: "unchanged",
    name: "Unchanged" },
  { key: "unreported",
    name: "Unreported" },
  { key: "all",
    name: "Total" }
  ],
  unresponsive: 0,
  failed: 0,
  pending: 0,
  changed: 0,
  unchanged: 0,
  unreported: 0,
  all: 0
}
```