#217 Basic Optical Flow

[Katherine Ann Scott]

Add support for optical flow between two images. The result can be of three forms
1. Flow tails (i.e. circles with tails and length all over the image)
2. Flow values (the flow values at each region of the image returned as a list of tuples).
3. The average flow of the image (magnitude and direction) -> scale the image first

http://opencv.willowgarage.com/documentation/python/video_motion_analysis_and_object_tracking.html?highlight=optical%20flow