Images with near-zero values do not appear

[aylward]

If an image has only small (near zero) intensity values, it is not rendered in 3D, but its 2D slices render correctly.

If the intensities are "large", itkWidgets.view() correctly shows an image

However, simply scaling that data to be near zero and again view-ing the results displays a blank 3D rendering

But the 2D rendering of the rescaled data does work as expected