Version build images
I think we should have a more granular control over versions in the build images.
Situation right now is that if we merge gitlab-omnibus-builder!33 (merged), we will probably break packages for earlier versions that cannot run correctly with go 1.7. I am sure we will have more similar situations with different other software. So I think we should start versioning build images.
I don't know about the versioning scheme but something like:
centos6:0.0.1
comes to mind.
What do you think @twk3 @balasankarc?