Bump version to 0.7.3
kamaki: ignore ssl certificates

Support kamaki 0.13rc5. From this version on, kamaki uses ssl
certificates by default. For now, instruct kamaki to ignore the
certificates.
Update ChangeLog and version files for 0.7.3
Merge pull request #28 from skalkoto/hotfix-0.7.3

Hotfix 0.7.3