Apply intensity windowing only to high-dynamic range images.
Apply intensity windowing only to high-dynamic range images.

Documentation said we apply intensity windowing only to high-dynamic
range images, but it was applied to all images including those with
low-dynamic range (intensities in [0,255]). Added conditional so that
the code and documentation are in sync.

InsightSoftwareConsortium/SimpleITK-Notebooks,InsightSoftwareConsortium/SimpleITK-Notebooks,zivy/SimpleITK-Notebooks,InsightSoftwareConsortium/SimpleITK-Notebooks,zivy/SimpleITK-Notebooks,zivy/SimpleITK-Notebooks