added email reminder documentation
added email reminder documentation

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