message: Simplify push_back
  Both types are now Vector3f.
diff: @@ -246,8 +246,7 @@ inline Mesh read_obj(std::string filename)
  { // matching with a space so that it doesn't match 'vt'
  auto vertex_data =
  detail::parse_vertex(line.substr(2)); // pass the string without the first two characters
  - mesh.vertices.push_back(
  - Eigen::Vector3f(vertex_data.first[0], vertex_data.first[1], vertex_data.first[2]));
  + mesh.vertices.push_back(vertex_data.first);
  if (vertex_data.second)
  { // there are vertex colours:
  mesh.colors.push_back(vertex_data.second.value());
  