plataformatec/devise — pull request #2371 by tomasv (2013-04-12 13:26:59+00:00)
Title: Fix devise sender bug with custom devise mailers.

The devise sender detection must take into account that the default
sender set in the custom devise mailer can be a proc.

```ruby
class CustomMailer < Devise::Mailer
default from: -> { 'custom@example.com' }
end
```

This breaks the mailer, the lambda is passed to the delivery mechanism as is and it breaks.