Entries are marked as read with the "entry-read" CSS class as soon as the user clicks on them, instead of waiting until the open animation finishes.
Added acceptance test to check that an alert is shown if there is a problem marking an entry as read.
Created two new support functions for acceptance tests. The new functions encapsulate logic that checks that an alert div is shown (and automatically hidden after 5 seconds) and that it is hidden, respectively.

Changed existing acceptance tests to use these functions to check the presence or absence of alerts under certain conditions, instead of repeating the logic over and over again. DRY is good!