Obj2mjcf

What's Changed
* Added overwrite option to cli, for simpler automation by nicolas-schreiber in https://github.com/kevinzakka/obj2mjcf/pull/9

New Contributors
* nicolas-schreiber made their first contribution in https://github.com/kevinzakka/obj2mjcf/pull/9

**Full Changelog**: https://github.com/kevinzakka/obj2mjcf/compare/v0.0.18...v0.0.19

You can now downsample textures via `texture-args.resize-percent`. It specifies the downsampling size as a percentage of the original size.

Fixes a bug that occurred when saving an MTL file.

Fixes a bug in Python 3.7.

Fix visual artifacts in texture (tweaked a setting in `trimesh`). Generated meshes look much better!

Better material parsing.