Carousel: Set proper offsets when device viewport changes size

In Mobile Safari, the carousel images will not stay in the correct positions when the device orientation is changed. For example, when the user changes from portrait to landscape view, the current slide is positioned to left instead of centered. Since the offsets are defined in terms of absolute pixels, they don't get updated automatically.

This problem also happens on the desktop versions of Chrome and Firefox.  When the browser window is resized, the offsets are no longer correct.

The solution for all these browsers is to reset the offsets when the `resizeTimeout` fires. This works for mobile too because the the orientation change triggers a resize event.