Made add_attachment migration compatible with old Rails / Rake versions.
Made add_attachment migration compatible with old Rails / Rake versions.

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