Error messages displayed by Rails or by Devise close automatically after 5 seconds.
Text that indicates the time to automatically close alert messages is inside an <em>.

This helps differentiate between the timer and the actual alert text.
When clicking on a feed with no entries, a notice is shown.

This notice is internationalized using Rails i18n helpers, instead of being composed with javascript as we did previously; it's easier to do i18n server-side with Rails than client-side with javascript.

The notice closes itself automatically after 5 seconds.