Request: Access to the sortable instance

I would like to be able to call methods on the sortable instance from inside my component, which I believe means we would need to passed in the instance as a prop.

Use case: being able to set options after the fact, based on certain conditions. For example: disabling sorting based on a toggle requires a call to `sortable.set('disabled', true)` which necessitates access to the sortable instance. 
