* Hack: move unit tests to a different source image, to work around issues when docker-ut has more than 1 tag.
Bump version to 0.4.7
* Hack: change builder tests to always use the current unit test image, instead of hardcoding 'docker-ut'
Merge pull request #1065 from dotcloud/bump_0.4.7

Bump version to 0.4.7
Documented release process for maintainers in hack/RELEASE.md