Tweaks to Pythonic Image.
Tweaks to Pythonic Image.

Use matplotlib image.aspect 'equal' so the aspect ratio is display properly
for the sliced images.

Delete some empty cells.

Update the nbformat to 4.

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