Circular reference

``` javascript
MeteorSettings.setDefaults({ public:
  { blog:
    { pictures: {
        maxWidth : 800,
        maxHeight : 800
      }
    }
  }
});
```

results in 

```
Uncaught Error: Circular reference found at: maxHeight:800
```

[Thrown here -  settings.js#L53](https://github.com/ogourment/settings/blob/master/src/settings.js#L53)

Any ideas?
