Update kept to work with the new daybed.js

This uses the new daybed.js API and works with kept to share the dashboards, using a hash in the url.
We might have to choose a way to indent then() consistently...
I think I prefer this way: 

```
return Daybed.startSession(self._options.host, {
    token: this._options.token
  })
  .then(function(session) {
    // ...
  });
```