implement Gravatar

[JohnRDOrazio]

it's really too early for this just yet, but I figure I'll jot it down to keep it in mind. In the models that are being generated from the new wiki page [[]], users can have an avatar. If we do start implementing avatars in the user interface (which could be a nice touch), we could also consider implementing Gravatar (not sure how many people outside of WordPress users have a Gravatar account, but hey it's out there, why not give this possibility).

Doesn't actually seem too difficult to implement: https://guides.railsgirls.com/gravatar