Complete README's 0.11 > 0.12 upgrade process.
Complete README's 0.11 > 0.12 upgrade process.

Install generator needs to be run again to create
"mailboxer_conversation_opt_outs" relation.

jason-wang-0401/mailboxer,jason-wang-0401/mailboxer,Groovej/mailboxer,Groovej/mailboxer,untitledstartup/mailboxer,joshtate04/mailboxer,mailboxer/mailboxer,mailboxer/mailboxer,lacco/mailboxer,mattherick/mailboxer,cantonyselim/mailboxer,Design-Collective/mailboxer,chepri/mailboxer,div/mailboxer,shekibobo/mailboxer,untitledstartup/mailboxer,shekibobo/mailboxer,sai43/mailboxer,t27duck/mailboxer,chepri/mailboxer,lacco/mailboxer,netbrick/mailboxer,jarkadlec/mailboxer,Design-Collective/mailboxer,roomaroom/mailboxer,sai43/mailboxer,netbrick/mailboxer,mattherick/mailboxer,roomaroom/mailboxer,joshtate04/mailboxer,jarkadlec/mailboxer,afalone/mailboxer,modsaid/mailboxer,t27duck/mailboxer,techstars/mailboxer,modsaid/mailboxer,cantonyselim/mailboxer