Update docs on using external registry with gitlab
Update docs on using external registry with gitlab

t-zuehlsdorff/gitlabhq,iiet/iiet-git,jirutka/gitlabhq,jirutka/gitlabhq,stoplightio/gitlabhq,iiet/iiet-git,axilleas/gitlabhq,axilleas/gitlabhq,mmkassem/gitlabhq,dreampet/gitlab,stoplightio/gitlabhq,jirutka/gitlabhq,stoplightio/gitlabhq,stoplightio/gitlabhq,jirutka/gitlabhq,t-zuehlsdorff/gitlabhq,dreampet/gitlab,axilleas/gitlabhq,dreampet/gitlab,mmkassem/gitlabhq,t-zuehlsdorff/gitlabhq,iiet/iiet-git,mmkassem/gitlabhq,mmkassem/gitlabhq,axilleas/gitlabhq,t-zuehlsdorff/gitlabhq,iiet/iiet-git,dreampet/gitlab