Addresses issue #2283. As documented in Matplotlib's interactive guide, show needs to be called without blocking the thread. When run in non-interactive mode, the default behavior of show() is to block the loop until all windows are closed.

Also fixes the frames being shown with the color channels in the incorrect order (VideoReader returns RGB frames, imshow expects RGB frames, and the channels were being swapped as if the frames were BGR).

This fix was tested on OS X.