Fix window not disposing bug.

Previously, exiting the window generated by OpenCV seemed to only hide
the window, but not destroy it. As a result, the program would get stuck
in an infinite loop. This commit resolves the problem on Windows 7, but
needs further testing.
Apply blur to background image display.

This matches the blurring that is applied before segmentation, resulting
in a more accurate display.
Merge pull request #9 from vancezuo/gui

Gui branch merged.