GitLab CI is now integrated in GitLab. The last 'stand-alone' version of GitLab CI was version 7.14. The sole purpose of GitLab CI 8.0 is to help you migrate data from your existing (pre-8.0) CI server into GitLab 8.0.
The migration procedure is documented in GitLab.
Please see the GitLab CI page on the website for all information.