[fixes #11]] merges all cubes into a single mario mesh
  * our problem was that we were trying to merge the GEOMETRY of each cube
    to the mesh. what we should have been doing is merging the MESH. sigh.
    * this totally slipped my mind. a geometry is just has all the points and
      faces for the shape, which is why it wasn't rendering for us.
    * from the docs: A mesh is an object that takes a geometry, and applies a
      material to it, which we then can insert to our scene

TODO
  * currently, mario is neon green. we should probably change that
      * we need to figure a way to apply the correct color to each cube
        in our merging loop

STRETCH
  * only merge specific parts of mario's body so that we can animate each
    chunk individually when he jumps! (ie. head/torso/arms/legs)