docs: Fix a typo.
Issue: LIBCLOUD-466 Add ingress/egress VPC support to security group rules.

Signed-off-by: Tomaz Muraus <tomaz@apache.org>
Move "private" method to the end, add a docstrings.
Update CHANGES.
Fix indentation.
Fix test failure in Python 2.5; enumerate in 2.5 doesn't support start argument.