Log the IP address used to create an account.

db/migrate/016_add_creation_ip.rb

@@ -0,0 +1,9 @@
+class AddCreationIp < ActiveRecord::Migration
+  def self.up
+    add_column "users", "creation_ip", :string
+  end
+
+  def self.down
+    remove_column "users", "creation_ip"
+  end
+end