message: Also invert the y axis of the uv coordinates in write_obj(...)
  Previously we only inverted them in write_textured_obj(...). I believe this was an oversight, since when using write_obj(...), one would rarely use the uv coords.
diff: @@ -67,7 +67,8 @@ inline void write_obj(Mesh mesh, std::string filename)
  {
  for (auto&& tc : mesh.texcoords)
  {
  - obj_file << "vt " << tc[0] << " " << tc[1] << std::endl;
  + obj_file << "vt " << tc[0] << " " << 1.0f - tc[1] << std::endl;
  + // We invert y because MeshLab's uv origin (0, 0) is on the bottom-left
  }
  }
  