examples: Add cnu example

This shows how cnucnu is used to retrieve the ovirt-node-iso version
from a webpage.

Signed-off-by: Fabian Deutsch <fabiand@fedoraproject.org>
Use unicode in more places

Previously verw raised an exception in cases where git raied an error
message containing non-ascii characters (e.g. the german sentence
"Ungültiger Objekt-Name" [invalid object name]).

To prevent the exception we now assume and tell python that it's utf8,
to help it decoding the blob.

Signed-off-by: Fabian Deutsch <fabiand@fedoraproject.org>