add preferences and customization (#171)

db/migrate/20170510175654_add_attachment_background_to_users.rb

@@ -0,0 +1,11 @@
+class AddAttachmentBackgroundToUsers < ActiveRecord::Migration
+  def self.up
+    change_table :users do |t|
+      t.attachment :background
+    end
+  end
+
+  def self.down
+    remove_attachment :users, :background
+  end
+end