[#11] successfully renders mario after merging geometries
  * reverted from version 61 to 58 in order to use .setMaterialIndex
  * MeshFaceMaterial's use case seems to usually be for people who want to
    set a different color/material to each face of a cube. however, i think
    using .setMaterialIndex() lets us attach an index to each cube itself,
    instead of each face of every cube.