Fixed an issue with multiple transitions in the carousel

The call to `.emulateTransitionEnd` failed when more than one
transition was used, as `.css('transition-duration')` would return a
comma-separated list (e.g. `".6s, 2s"), which would then be passed as
`NaN`. This commit fixes the issue, by passing the list to
`findDuration`, which returns the highest duration as milliseconds.
The fix won't break any existing use of `.emulateTransitionEnd`, as
integers are ignored.