Updated README to make pypi happy

Proper handling of image names

Even more logging fixes + do not squash if not necessary

Reworked CLI options with defaults

Only image name to squash is required now, everything else is optional.

Resulting tag for the squashed image will be the original image name
provided with the 'image' argument.

By default all layers will be squashed besides the base (FROM) image.

Make sure the generated layer ID is not integer when shortened

Fixes goldmann#10