This script adds unread notifications count in the tab title in Twitter.
eg. (in timeline) instead of
(1) Twitter, it becomes
3 | (1) Twitter
where 3 is the unread notifications count and (1) the default unread tweets count.
Note: there has been a recent change in Twitter's layout, and so, whenever you have new more than 20 unread tweet in your timeline, the unread tweets count (in the 'See 2 new Tweets' button as well as in the tab title) is changed into an asterisk, and after that, there's no unread count value available in the page code, for the script to use.
Since v3 it uses the excellent library arrive.js
Thanks a lot to wOxxOm for his valuable help in here.