Move bubbles with translate rather than position (Issue #1)

Resolves #1.  

Still some more work to do though to fix animations.

* Parallax effect - Uses background-position which causes jankyness.  Can probably move the background to its own layer (not body), and translate it around.  There was a case study on flickr for this recently.
* Mouseover bubble popping effect - Animates on width.  We can probably use scale here instead.