Update README.md: added sudo usage
Update README.md: added sudo usage

Since docker 0.5.2 sudo is required:
http://blog.docker.io/2013/08/containers-docker-how-secure-are-they/#specific-attack-surface-of-the-docker-daemon

> now uses a UNIX socket instead of a TCP socket bound on 127.0.0.1
stormerider/rancher-wpmu-nginx-trusty,zhanggangbz/docker-wordpress-nginx,eugeneware/docker-wordpress-nginx,Sam-R/docker-octobercms-nginx-ssh,HouseOfAgile/docker-wordpress-multilang-nginx,omusico/docker-octobercms-nginx-ssh,avoltusfi/docker-drupal-nginx,lingz/docker-wordpress-nginx,technowar/docker-wordpress-nginx,jamiehannaford/docker-wordpress-nginx,xiongjungit/docker-wordpress-nginx,imcaffrey/docker-wordpress-nginx,stormerider/rancher-wpmu-nginx-trusty,fpinzn/docker-wordpress-nginx,stormerider/docker-nginx-php-fpm,nixelsolutions/docker-wordpress-nginx,jpgarretson/docker-wordpress-nginx,beacloudgenius/docker-wordpress-nginx,susanna8930/docker-wordpress-nginx,micks80/wordpress-docker-ecr,lymanlai/docker-wordpress-nginx,insfere/docker-wordpress-nginx,jancarloviray/docker-wordpress-nginx,alexeymasolov/docker-octobercms-nginx-ssh,stormerider/docker-wpmu-nginx,stormerider/docker-wpmu-nginx,jamiehannaford/docker-wordpress-nginx,rija/docker-wordpress-nginx,acaveroc/docker-wordpress-nginx,stormerider/rancher-wordpress-nginx-trusty,daimajia/docker-wordpress-nginx,fluential/docker-wordpress-nginx-lowmem,y16ra/docker-wordpress-nginx,jamesmarva/docker-wordpress-nginx