GitLab is now simple to install

What this post added

Introduced three new simplified installation options: an official GitLab Chef cookbook, GitLab Packer virtual machines, and GitLab Omnibus packages. The Omnibus packages, built using `omnibus-ruby`, allow for installation with a single command (`apt-get install -y openssh-server postfix dpkg -i gitlab_6.6.0.pre1.omnibus.2-1.ubuntu.12.04_amd64.deb gitlab-ctl reconfigure`). Initial Omnibus packages have reduced feature support (e.g., no application backups or HTTPS).