message: make compilable with g++ 4.8
diff: @@ -829,7 +829,7 @@ std::string cnn_visualization::get_xyz_from_index(int index, bool rec) {
  {
  std::stringstream mol_stream;
  std::string line;
  - mol_stream = std::stringstream(lig_string);
  + mol_stream.str(lig_string);
  while (std::getline(mol_stream, line))
  {
  if(boost::algorithm::starts_with(line, "ATOM")
  @@ -844,7 +844,7 @@ std::string cnn_visualization::get_xyz_from_index(int index, bool rec) {
  }
  }
  - mol_stream = std::stringstream(rec_string);
  + mol_stream.str(rec_string);
  while (std::getline(mol_stream, line))
  {
  if(boost::algorithm::starts_with(line, "ATOM")
  @@ -874,9 +874,9 @@ std::string cnn_visualization::get_xyz_from_index(int index, bool rec) {
  //fill in map with a mapping from xyz coordinates (pdb foramt) to atom serial number (pdb)
  //clears map
  void cnn_visualization::populate_coordinate_map(const std::string& molstring, std::unordered_map<std::string, int>& map) {
  - std::stringstream mol_stream;
  + std::stringstream mol_stream(molstring);
  std::string line;
  - mol_stream = std::stringstream(molstring);
  +
  map.clear();
  while (std::getline(mol_stream, line))
  {
  