readme: use coinbase link
readme: use coinbase link

maqsoodumt/docker-squid,sameersbn/docker-squid,boliu83/docker-squid,opendoor-labs/docker-squid-s3,korczis/docker-squid-rubygems-proxy,Optibus/docker-squid,korczis/docker-squid-rubygems-proxy,zultron/docker-provisioning,linearregression/docker-squid-s3