message: Small changes suggested by Marc
diff: #include <algorithm> // for std::max
  #include <random>
  #include <cassert>
  +#include <cmath>
  namespace Gudhi {
  @@ -1044,9 +1045,7 @@ class Cover_complex {
  }
  for (auto const& simplex : simplices) {
  - // Add simplices
  - st.insert_simplex_and_subfaces(simplex);
  - // Add cone on simplices
  + // Add a simplex and a cone on it
  std::vector<int> splx = simplex;
  splx.push_back(-2);
  st.insert_simplex_and_subfaces(splx);
  @@ -1070,7 +1069,7 @@ class Cover_complex {
  else
  st.assign_filtration(simplex, filts);
  }
  - std::vector<int> magic = {-2};
  + int magic[] = {-2};
  st.assign_filtration(st.find(magic), -3);
  // Compute PD
  @@ -1084,7 +1083,7 @@ class Cover_complex {
  for (int i = 0; i < max_dim; i++) {
  std::vector<std::pair<double, double> > bars = pcoh.intervals_in_dimension(i);
  int num_bars = bars.size();
  - std::cout << num_bars << " interval(s) in dimension " << i << ":" << std::endl;
  + if(verbose) std::cout << num_bars << " interval(s) in dimension " << i << ":" << std::endl;
  for (int j = 0; j < num_bars; j++) {
  double birth = bars[j].first;
  double death = bars[j].second;
  @@ -1212,8 +1211,8 @@ class Cover_complex {
  }
  if (type == "Nerve") {
  - for (std::map<int, std::vector<int> >::iterator it = cover.begin(); it != cover.end(); it++)
  - simplices.push_back(it->second);
  + for(auto& simplex : cover)
  + simplices.push_back(simplex.second);
  std::sort(simplices.begin(), simplices.end());
  std::vector<std::vector<int> >::iterator it = std::unique(simplices.begin(), simplices.end());
  simplices.resize(std::distance(simplices.begin(), it));
  