message: Slightly simplify obj grammar
diff: @@ -91,11 +91,11 @@ struct obj_grammar
  boost::spirit::qi::rule<It, vec3(), skip_t> r_ke;
  boost::spirit::qi::rule<It, vec3(), skip_t> r_ks;
  boost::spirit::qi::rule<It, float(), skip_t> r_ns;
  - boost::spirit::qi::rule<It, string(), skip_t> r_map_kd;
  + boost::spirit::qi::rule<It, sref_t(), skip_t> r_map_kd;
  // obj rules
  - boost::spirit::qi::rule<It, sref_t()> r_comment;
  + boost::spirit::qi::rule<It> r_comment;
  boost::spirit::qi::rule<It, sref_t(), skip_t> r_mtllib;
  boost::spirit::qi::rule<It, sref_t(), skip_t> r_usemtl;
  