[Enhancement] Show summary information when hovering an avatar

[Contribucious]

Can be cool to have summary information when hovering an avatar with the mouse.
=> See this screenshot: http://i.imgur.com/rjJjwUm.png

- Name (here defined as "Security SE")
- Location (here defined as "The Stack Exchange network")
- Number of tweets
- Number of following
- Number of followers
- Number of listed

Of course, this order can be changed or we can even have some more information (the bio for example) but I think it's already just what we often need to know (who they are > Name, where they are > Location, …).