StyledLayer.sharedStyleId does not link style in Sketch inspector
The follow works as expected
```javascript
var layer = new Shape({})
layer.sharedStyle = sharedStyle
layer.style.syncWithSharedStyle(sharedStyle)
```

Using `sharedStyleId` however seems to miss something causing the Sketch inspector panel to not show the linked style. 
```javascript
var layer = new Shape({})
layer.sharedStyleId = sharedStyle.id
layer.style.syncWithSharedStyle(sharedStyle)
```

Looking the implementation I'm not sure why this would happen. They appear to do the same thing under the hood. Maybe sending different String types to `this._object.setSharedStyleID(<id>)`?