Implement prefabs and camera follow controls.

This commit implements the prefab registration/creation system and
adds some minor fixes and implementation details to the "follow"
component. This commit is not build ready, as it will be branched
to add a much needed update of the THREE.js libraries.
Upgrade THREE to r60 and fix camera.

This commit updates THREE.js to its most recent revision and fixes
a bug where entities with the follow component would encounter gimbal
lock if the offset placed them directly above the target. This was due
to the call to THREE.Camera#lookat() in the target setter.
Implement prototype for amoeba movement.

This commit adds a prototypical amoeba to the scene. This is just
one idea for how we might use physical objects to mimic the movement
of an amoeba.
Make main camera globally accessible.

This commit makes the main scene camera globally accessible in a
sane manner by setting Entity.Camera.main to the first instance of
Entity.Camera that is created. Obviously, this may be overridden by
the user at any point if they wish to specify the main camera.
Implement interface component.

This commit adds the interface component which allows the user to
create DOM-based GUI elements anchored to the owner's screen position.
It also adds jQuery to the vendor libraries.
Merge branch 'master' of https://github.com/dkushner/amoebadome