Carousel fix

Fix several carousel bugs and other minor things.
- fix strange jquery carousel jumping
- account for carousel items having margins
-  $().Uranium() can be run multiple times without re-initializing widgets
- read `"data-ur-translate3d"` attribute to enable/disable translate3d()
- events `slidestart.ur.carousel` and `slideend.ur.carousel` triggered are now namespaced
- bring back global `Uranium` object
  - e.g. Uranium.carousel[1] has methods like `jumpToIndex()` and fields like `itemIndex` and `count`