Add unzip as installation depedency
We need Info-ZIP's unzip for GitLab-EE in order to support: https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/117 (support for ZIP artifacts in GitLab Pages)
The package is named: unzip
both on Debian and CentOS:
CentOS 6.5:
Package unzip-6.0-2.el6_6.x86_64 already installed and latest version
CentOS 7.0:
Package unzip-6.0-15.el7.x86_64 already installed and latest version
Debian 7.x:
UnZip 6.00 of 20 April 2009, by Debian. Original by Info-ZIP.
/cc @marin