Feature request - access to root xib view

From your readme:
```
final class MyCustomWidget: UIView, NibOwnerLoadable {
…
required init?(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
self.loadNibContent()
}
}
```

The problem is I loose a link to xib root view and can access it via `MyCustomWidget().subviews` property only or by making a link to this view manually each time.

Why it is required? For example, I create a subview with labels which should be added to a view controller with a dark background. So I make subview's background dark in xib (to see light labels) and change this color back in runtime.