Better command-line docs for renew.
Better command-line docs for renew.

DavidGarciaCat/letsencrypt,DavidGarciaCat/letsencrypt,jsha/letsencrypt,dietsche/letsencrypt,jtl999/certbot,thanatos/lets-encrypt-preview,dietsche/letsencrypt,jsha/letsencrypt,bsmr-misc-forks/letsencrypt,brentdax/letsencrypt,wteiken/letsencrypt,TheBoegl/letsencrypt,mitnk/letsencrypt,thanatos/lets-encrypt-preview,lmcro/letsencrypt,bsmr-misc-forks/letsencrypt,letsencrypt/letsencrypt,stweil/letsencrypt,letsencrypt/letsencrypt,stweil/letsencrypt,brentdax/letsencrypt,wteiken/letsencrypt,jtl999/certbot,lmcro/letsencrypt,mitnk/letsencrypt,TheBoegl/letsencrypt