message: Use contiguous_vertices in find_simplex().
diff: @@ -531,7 +531,20 @@ class Simplex_tree {
  Siblings * tmp_sib = &root_;
  Dictionary_it tmp_dit;
  Vertex_handle last = simplex.back();
  - for (auto v : simplex) {
  + auto vi = simplex.begin();
  + if (Options::contiguous_vertices) {
  + GUDHI_CHECK(contiguous_vertices(), "non-contiguous vertices");
  + Vertex_handle v = *vi++;
  + if(v < 0 || v >= static_cast<Vertex_handle>(root_.members_.size()))
  + return null_simplex();
  + tmp_dit = root_.members_.begin() + v;
  + if (!has_children(tmp_dit) && v != last) {
  + return null_simplex();
  + }
  + tmp_sib = tmp_dit->second.children();
  + }
  + for (; vi != simplex.end(); ++vi) {
  + Vertex_handle v = *vi;
  tmp_dit = tmp_sib->members_.find(v);
  if (tmp_dit == tmp_sib->members_.end()) {
  return null_simplex();
  