Prevent swipes from bubbling to parent elements

[shicks]

Currently if a swipeable container is contained in some other swipeable element, swiping an inner-nested element causes both containers to swipe. By stopping propagation after a successful track event, this undesired behavior is prevented.

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[shicks]

I signed it!

[shicks]

Let's try that again...

I signed it!

[googlebot]

CLAs look good, thanks!

[shicks]

Added a test, PTAL.

[notwaldorf]

LGTM, thanks!