Rectangle properties and functions do not work
The rectangle functions, that are used to modify layer frames do not work. I can read the values, but setting them has no effect.

```javascript
log(document.selectedLayers.layers[0].frame.height) // -> 200

document.selectedLayers.layers[0].frame.height = 100

log(document.selectedLayers.layers[0].frame.height) //  -> 200
``` 
Same for the `offset()` function.


Here's a temporary workaround: https://github.com/sketchplugins/plugin-requests/issues/17