Update CHANGES with 0.13.3 entry.
Issue LIBCLOUD-470: Add VPC Elastic IP support. This not only adds full EIP
support for EC2-Classic/VPC, but also adds a new ElasticIP abstraction
that will make future promotion into the base API much easier. New tests
were added to validate VPC association/disassociation/release calls work
as expected.

Closes #220.

Signed-off-by: Tomaz Muraus <tomaz@apache.org>
Update CHANGES.