Updated .gitignore to ignore the samples folder.
Added method to get a random crop from a image.
Changed var name from has_cv2 to use_cv2.

Also corrected identation problem in load_img method. Also, I'm
increasing to 255 the range when skimage returns gray image between
0 and 1.

Also created new methods to convert rgb2gray and bgr2gray and
gray2bgr.
Added way to start from a given index when loading

.. images from dir.
Added VideoIter class.