Added getter in Tracker for TrackedObject::lastSeen. Useful for knowing if you're getting an actual object (lastSeen == 0) or its persistent shadow (lastSeen > 0).
Merge branch 'master' of github.com:prisonerjohn/ofxCv

# By George Profenza (2) and others
# Via Kyle McDonald (3) and orgicus (1)
* 'master' of github.com:prisonerjohn/ofxCv:
  fixed gray grabber bug in example, closes #113
  removing RateTimer
  ObjectFinder.update() takes grayscale images into account
  allow grayscale image to be tracked
  allow grayscale image to be tracked