Make this project a gem
The gem should have a simple API that provides a #templates_base_dir
method, so that it can be plugged nicely into Gitlab::Template::GitlabCiYmlTemplate#base_dir
(https://gitlab.com/gitlab-org/gitlab-ce/blob/120c79020ddd3097ae64149c75864353276aaa5f/lib/gitlab/template/gitlab_ci_yml_template.rb#L23).