rails/rails — pull request #16836 by camelmasa (2014-09-08 10:23:21+00:00)
Title: Add support for multiple preview_path

Hi guys.

I'd like to add support for multiple preview_path of ActionMailer. (It could configure only one directory path now.)

Because I think I'd like to configure it in Rails Engine.

For example.

```rb
initializer "spree.core.mailers_previews" do |app|
app.config.action_mailer.preview_path << File.join(root, "test", "mailers", "previews")
end
```