Feature request, additional "targetingOnly" argument on "fromEvent()".

"targetingOnly" specifies whether to cancel the event if processed during the targeting phase (targetingOnly = true), or allow it to bubble up the display list for other listeners to process.
Changes the behavior of the targetingOnly boolean. If targetingOnly is true, bubbling is canceled, but the observer is only notified if the event's phase is AT_TARGET.
Merge pull request #6 from guyinthechair/master

Feature Request: Additional "targetingOnly" Boolean argument in "Observable.fromEvent" and "Observable.fromEvents".