Move unread-related functions from zulip.js to unread.js.

(imported from commit efc0dd84c2cd30b0203b906af6991475d8a63985)

static/js/notifications.js

@@ -45,7 +45,7 @@ exports.initialize = function () {
 
         // Update many places on the DOM to reflect unread
         // counts.
-        process_visible_unread_messages();
+        unread.process_visible();
 
     }).blur(function () {
         window_has_focus = false;