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/schedules/_schedule_item.html.haml

@@ -10,8 +10,7 @@
       = event.title
 
     - event.speakers_ordered.each do |speaker|
-      = image_tag speaker.gravatar_url, :class => "img-circle pull-right speaker-pic", |
+      = image_tag speaker.profile_picture, :class => "img-circle pull-right speaker-pic", |
                                         :alt => speaker.name, |
                                         :title => speaker.name, |
                                         :style => "height: #{ speaker_height(@rooms) }px; width: #{ speaker_width(@rooms) }px;"
-