Add support for GitLab CE 6.9
gitlab-shell will talk to Unicron instead of nginx

Separate nginx instance was needed to avoid using encrypted SSL
connection between gitlab-shell and GitLab on localhost. This
modification is now dropped and gitlab-shell will talk do unicorn
(internal GitLab webserver) directly.
Merge pull request #77 from drybjed/role/gitlab

Updates in 'gitlab' role, support for GitLab 6.9