Carousel fix

Fix several carousel bugs and other minor things.
- fix strange jquery carousel jumping
- account for carousel items having padding (in the future maybe margins as well)
- properly allow different width items
- automatically use minimum number of clones needed
- can wait for late-loaded images to load
- swipe direction determines which direction carousel snaps to
- easier to insert new carousel items after initialization
-  $().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 `count`
- attempted to clean up code, slightly prepare for future features