Dispatch to parents

Ok, here is the bubbling dispatchToParents method, with tests.
Took the liberty to add a little feature: stopPropagation set to true in payload by any ancestor stops further bubbling. If one ancestor needs to catch the event and do the job, why bother its ancestors (and waste time) with useless triggers? 

Cool feature is that since the same object is passed along as payload, data can easily be sent back to issuer or shared between ancestors. Feel free to improve or to let me know if I missed something.
Let's go with `propagationDisabled`.  Please add it to the docs, and maybe also include a little description about why we gave it such a funny name (to avoid ambiguity with the `stopPropagation` function)

Thanks @mmikeyy !