message: using local json instead of system path
diff: #include <fstream>
  #include <stdexcept>
  #include <string>
  -#include <tfn_lib/tfn_lib.h>
  -#include "json/json.h"
  +#include "tfn_lib/tfn_lib.h"
  +#include "tfn_lib/json/json.h"
  namespace ospray {
  namespace sg {
  