Support Users Directly Uploading Profile Pictures.

* Adds a `picture` attribute to `User`.
* Preserves Gravatar as a fallback option.
* Now, you should use `user.profile_picturer` instead of `gravatar_url`
* TODO: Ensure `profile_picture` handles sizing right for uploaded images.

app/views/users/edit.html.haml

@@ -10,8 +10,16 @@
         = f.input :nickname, as: :string, hint: 'This is how the other users see you, not your real name'
         .control-label
           = "Avatar"
-        = image_tag(@user.gravatar_url(size: '48'), title: "Yo #{@user.name}!", alt: '')
+        = image_tag(@user.profile_picture(size: '48'), title: "Yo #{@user.name}!", alt: '')
         = link_to 'Change your avatar here', 'https://gravatar.com'
+      %br
+        %p
+          Or upload a picture.
+        = image_tag f.object.picture.thumb.url if f.object.picture?
+        - if @user.picture?
+          = image_tag(@user.picture.thumb.url, width: '20%')
+        = f.input :picture, hint: 'If you upload a picture, it will be used in place of Gravatar.'
+
         = f.input :affiliation, as: :string,
           hint: 'This could be a company, a user group, or nothing at all.'
         = f.input :biography, input_html: { rows: 5, data: { provide: 'markdown' } },