Adapt GitLab to 5.1pre (uses puma instead of unicorn).

Update submodules.

M  gitlab/config.yml.tpl:
  add http_settings for latest GitLab 5.1 config
M  gitlab/github:
  Latest 5.1 commit
M gitlab/gitlab-shell:
  Latest 1.2.x commit
M  gitlab/gitlab-shell_replace:
  Only replace 'http.use_ssl' once
M  gitlab/gitlab-shell_restore
  Only restore 'http.use_ssl' once
M  gitlab/gitlab.yml.tpl:
  Update to latest gitlab.yml content
M  gitlab/gitlabd:
  Uses puma
M  gitlab/install_or_update_gitlab.sh.tpl:
  Uses right installation commands
A  gitlab/puma.rb.tpl:
  ADD puma config file, with correct application_dir
 D gitlab/unicorn.rb.tpl:
  DELETE any unicorn reference