Avatar Tooltip plugin: how to show only user bio and social links

Here you are a piece of code to customize the content shown with Avatar Tooltip plugin.
You can paste the following code in a php file (named as you like) and put it inside /wp-content/mu-plugins folder of your blog (if mu-plugins does not exist, simply create it).

This code replaces the standard tooltip content with the user bio (description), link to user recent posts, links to social network profiles (as filled in profile by user).
It creates new contact fields (Twitter, Facebook, Linkedin, Google+) in user profile, so each user can fill them. The tooltip gets nothing from Gravatar profile.