title: Rails 3, Devise: change flash message on user registration
body: <p>When users sign up, they have to confirm because I enabled the confirmable module of Devise.  This is the message they see:</p>
  
  <pre><code>You have signed up successfully. However, we could not sign you in because your account is unconfirmed.
  </code></pre>
  
  <p>I checked the locale file and tried making some modifications:</p>
  
  <pre><code>registrations:
    signed_up: 'Welcome! You have signed up successfully.'
    inactive_signed_up: 'You have signed up successfully. However, we could not sign you in because your account is %{reason}.'
    ...
    reasons:
      inactive: 'inactive'
      unconfirmed: 'awaiting email confirmation.  Please check your email'
  </code></pre>
  
  <p>Is there a way to have <code>%{reason}</code> reference the message of reasons.unconfirmed instead of just using "unconfirmed"?</p>