Add compatibility with three.js r66

three.js changed their geometries to use Face3 (since Face4 was removed), so minecraft-skin's UV mapping was broken with r66. This PR updates the UVs for three.js r66 compatibility, and preserves compatibility with r58 (or earlier) by using the Face4-based old UVs if `BoxGeometry` (new name for `CubeGeometry`, but both are available on r66; kept the old name for compatibility with r58) is not defined. Fixes GH-5

Note: this also includes pull request GH-9 (using three.js via NPM)