OUT/Rules.py: leading tabs -> fourspace conversion

Signed-off-by: Gregory M. Turner <gmt@be-evil.net>
scripts/init-upstream-tracking: fix missing imports

import NotARepository & InvalidOverlayRepositoryError from OUT.Repo correctly

Signed-off-by: Gregory M. Turner <gmt@be-evil.net>

squashme: import InvalidOVerlayRepositoryError too
s:wip-RulesEngine
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Update README with an example, requirements, and to reflect concept evolution

Signed-off-by: Gregory M. Turner <gmt@be-evil.net>