plataformatec/devise — pull request #2718 by ssendev (2013-11-01 20:54:59+00:00)
Title: Separate redirects and flash messages in navigational_formats and flashing_formats

With

```ruby
after_filter :add_flash_to_header_if_xhr
def add_flash_to_header_if_xhr
if request.xhr? && flash.present?
response.headers["X-Flash-Messages"] = flash.to_hash.to_json
flash.discard
end
end
```

it is desirable to get flash messages on formats that are not navigational. This patch adds a new option flashing_formats that allows to specify which formats should receive flash messages, by default it inherits the navigational_formats.