Add a 'Mark as read' function.

While I think it's important to keep Rososo as simple as possible I'd still like to have the option of marking some bookmarks as no longer fresh without following the actual link.

In a way I really dig how Rososo encourages you to have only those bookmarks you really want to visit, but sometimes I've already read the new content without following the Rososo link. Granted, I can visit, quickly return and then reload the page in a few seconds, but a simple button next to the "x" (maybe an "o"?) would help me achieve maximum peacefulness. :)

Thanks for listening, guys!