Added documentation for SMTP auth
Added documentation for SMTP auth

amoennin/elastalert,saltukalakus/elastalert,ltagliamonte/elastalert,rarescosma/elastalert,mash0304/elastalert,gbenoit79/elastalert,AlphaStaxLLC/elastalert,jetyang2005/elastalert,jetyang2005/elastalert,iamrudra/elastalert,megancarney/elastalert,thomdixon/elastalert,brianparry/elastalert,jetyang2005/elastalert,kkoppel/elastalert,saltukalakus/elastalert,rounds/elastalert,dvopsway/elastalert,lytics/elastalert,rprabhat/elastalert,Yelp/elastalert