readme clarity update.
bugfix: fixed specification and closure technique so a new add_visual function is made for each visual instead of overwriting all with the last discovered visual.
Update use-case specification and users to use image file visual instead of screenshot which requires an invasive monkeypatch.
Specified and updated implementation of behavior for adding visuals.
Updated specification and implementation for image property of visuals.
comment / code cleanup
Added fallback cv2.pyd in case windows users don't have opencv installed. Would like to have something for linus as well.
removed unused screenshot patch decorator
First use case green. Adding second use-case which involves chaining
images together to get a result.
Added new user data that is needed for chained visual use-case.
Specified and implemented feature descriptors property on base visual so
they are available for any visual. Needed for planned unique_object visual.
Second use-case specified, implemented, and green. Basically this confirms that
connections between visuals work.