for rails-3.0.0.beta4 with devise-1.1.rc2
_ the subject can be customized by editing the appropriate keys
config/locales/devise.en.yml
default key is 'devise.mailer.confirmation_instructions.subject'
note it's is possible to set model-specific subjects by adding a
corresponding key
devise.mailer.confirmation_instructions.user_subject'
_ the mail-from can be set in config/initializers/devise.rb by editing
config.mailer_sender = "please-change-me@config-initializers-
devise.com"