add a controller to return the url based on an email address
show the profile image in the profile page, updated as the email address changes
Merge pull request #295 from adrianbanks/gravatar

Fix #294 Make it more obvious that we use gravatar for the profile images.

This changes adds the profile picture to the edit profile page, with a note saying that we use gravatar. Additionally, when you edit the email address, the profile picture updates to reflect the email address change.