Add libravatars to some of the UI.
Add a template filter ``avatar`` that returns the html to the avatar
Drop the calling for the avatars from the controllers
Adjust the templates to use the new avatar filter
Add the avatars on the stats page
Fix the unit-tests now that there is the gravatar image next to the username
Merge pull request #75 from fedora-infra/libravatar_filter

Libravatar filter
Add the avatar on the pending ACLs page
Merge pull request #74 from fedora-infra/libravatar

Add libravatars to some of the UI.