Update README example with smtp and mailcatcher
Update README example with smtp and mailcatcher

Hi, i would suggest to add this patch, it's very helps me during testing. Sorry for bad English.
EdwardPantoja/mail,kert-io/mail,jonkgrimes/mail,jonkgrimes/mail,pjskennedy/mail,pushrax/mail,kert-io/mail,zacholauson/mail,smallspark/mail,pjskennedy/mail,0x00evil/mail,mikel/mail,jeremy/mail,kaineer/mail,zacholauson/mail,pascalbetz/mail,schepedw/mail,jeremy/mail,benmmurphy/mail,kjg/mail,kjg/mail,schneems/mail,schneems/mail,wktk/mail,smallspark/mail,benmmurphy/mail,wktk/mail,agaridata/mail,agaridata/mail,owenr/mail,jeremyevans/mail,carsonreinke/mail,carsonreinke/mail,missive/mail,EdwardPantoja/mail,kaineer/mail,planio-gmbh/mail,schepedw/mail,pushrax/mail,jeremyevans/mail,0x00evil/mail