Re-train a model.. about opennpd

[EvergreenHZ]

1. increase negRatio (say -negRatio 1.5) and decrease maxFAR (say -maxFAR 1e-8)
2. find a good threshold score in the test case (say float score = 10 instead of -1, see bellow)
   `int main(int argc, char* argv[])
   {

printf("************* [TEST] Npd:detect test... *************\n");

npd::npddetect npd;
npd.load(argv[1]);
cv::Mat img = cv::imread(argv[2], 0);
string savepath = "1.jpg";
float score = -1;  # change -1 to other number`