Use forwardRef to pass the ref up the component tree

I'm currently trying to expose slick to my component so I can use `.slick('resize')`.

However, the ref seems to return the ReactSlick instance itself and that doesn't seem to contain a ref to the slick instance.

React has a newish feature called [forwardRef](https://reactjs.org/docs/forwarding-refs.html) which enables a component to forward the ref down to the base component/node. Would be really useful to have this and expose the slick instance right the way up the tree.

Alternatively, does anyone know a way of exposing the slick instance or triggering the resize event?