Added help text for -d flag
Added help text for -d flag

lmcro/letsencrypt,VladimirTyrin/letsencrypt,lmcro/letsencrypt,brentdax/letsencrypt,thanatos/lets-encrypt-preview,Sveder/letsencrypt,wteiken/letsencrypt,mitnk/letsencrypt,goofwear/letsencrypt,lbeltrame/letsencrypt,dietsche/letsencrypt,letsencrypt/letsencrypt,DavidGarciaCat/letsencrypt,sjerdo/letsencrypt,TheBoegl/letsencrypt,jtl999/certbot,twstrike/le_for_patching,martindale/letsencrypt,dietsche/letsencrypt,VladimirTyrin/letsencrypt,mrb/letsencrypt,lbeltrame/letsencrypt,piru/letsencrypt,jsha/letsencrypt,bsmr-misc-forks/letsencrypt,DavidGarciaCat/letsencrypt,Sveder/letsencrypt,brentdax/letsencrypt,twstrike/le_for_patching,xgin/letsencrypt,bsmr-misc-forks/letsencrypt,stweil/letsencrypt,kuba/letsencrypt,jsha/letsencrypt,wteiken/letsencrypt,stweil/letsencrypt,kuba/letsencrypt,thanatos/lets-encrypt-preview,mitnk/letsencrypt,sjerdo/letsencrypt,martindale/letsencrypt,piru/letsencrypt,goofwear/letsencrypt,TheBoegl/letsencrypt,mrb/letsencrypt,letsencrypt/letsencrypt,jtl999/certbot,xgin/letsencrypt