feat(leap bind)

Enables easy binding of frame data to a scope.

```html
<div leap-bind="{hands: 'hands'}" 
       style="position:absolute;left:{{hands[0].palmPosition[0]}}px">{{hands[0].palmPosition[0]}}</div>

<div leap-bind="{hands: 'hands'}"
       leap-bind-update-rate="1000"
       style="position:absolute;left:{{hands[0].palmPosition[0]}}px">{{hands[0].palmPosition[0]}}</div>
```

@PascalPrecht have you time to review?