Ability to zoom

I love this module, by the way! What a fantastic addition it is to the Drupal ecosystem.

It would be great to have a zoom facility on the the split screen preview - often the preview in the a half-screen width iframe ends up being closer to what a tablet layout will look like - zooming out would give a more accurate idea of what the page will look like without having to go to the full screen preview. Or alternatively some means of selecting a device/screen width to emulate, so you can flick between desktop, tablet and mobile representations.