Librarification of keikan

[Tloru]

Right now, keikan is not a library. A lib.rs should be added, makescene should be moved to be a test, and the rendering code (render.rs) should be moved to more appropriate places (Like an impl on camera and scene, for instance).

[slightknack]

I've since moved the rendering code to more appropriate places, but I've yet to add a lib.rs and so on.