Update dr.js doc for interact.on/off
Delegate DOM events set by interact('selector').on

function log (event) {
    console.log(event.type, event.currentTarget);
}

interact('*').on('click', log);
interact('*').on('click', log, true);
// log will be called twice for every ancestor of event.target

useCapture flag is used however, capture phase order is not followed -
the listener will be called with the deepest element as the first
currentTarget.