added comments to contours.py and edge.py samples

samples/python2/contours.py

+'''
+This program illustrates the use of findContours and drawContours.
+The original image is put up along with the image of drawn contours.
+
+Usage:
+    contours.py
+A trackbar is put up which controls the contour level from -3 to 3
+'''
+
 import numpy as np
 import cv2
 
@@ -30,6 +39,8 @@ def make_image():
     return img
 
 if __name__ == '__main__':
+    print __doc__
+
     img = make_image()
     h, w = img.shape[:2]
 

samples/python2/edge.py

+'''
+This sample demonstrates Canny edge detection.
+
+Usage:
+  edge.py [<video source>]
+
+  Trackbars control edge thresholds.
+
+'''
+
 import cv2
 import video
 import sys
 
+
 if __name__ == '__main__':
+    print __doc__
+    
     try: fn = sys.argv[1]
     except: fn = 0