Added nonMaxSuppression to detect method

nonMaxSuppression wasn't working on a number of the master forks of PartsBasedDetector, because it was being called before the candidate vector had been filled.  I added it back with a allowed overlap of less than 40% which I found to work pretty well.  The allowed overlap can be changed by changing the third argument of nonMaxSuppression, the smaller the fraction, the less overlap allowed between candidates, the more candidates are suppressed.