Angularjs detecs read feeds by checking if they have <=0 unread entries, instead of ==0.

Normally unread entries should never be negative, but just in case...
After reading all entries in a feed, if the user clicks on the same feed again or on its folder, the feed does not disappear.

This intended to eliminate the weird behavior in which sometimes the user was left with a "no entries" message for a feed which was already removed from the sidebar.