Improving explanation of indexing.
Improving explanation of indexing.

Improve the explanation illustration the difference between SimpleITK
image and numpy array indexing and access to channel information.

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