colinta/motion-firebase — pull request #10 by markrickert (2014-10-20 04:44:41+00:00)
Title: Start at end at

These three methods can take nil as their priority according to the documentation. Let's just default to that since some of the docs do stuff like this:

```javascript
scoresRef.endAt().limit(10).once('value', function(snap) {
// etcetera, etcetera
});
```