Update for gl-matrix voxel-physical

Changes to use gl-matrix-style vector arrays instead of three.js-style objects. Depends on a corresponding change to voxel-physical: https://github.com/chrisdickinson/voxel-physical/pull/11

Using this in the voxel-engine PR to replace three.js with ndarray/gl-now: https://github.com/maxogden/voxel-engine/pull/103