Fix regression in fb9c903a where objects were no longer frozen upon delete

lib/paranoia.rb

@@ -10,6 +10,7 @@ module Paranoia
   def destroy
     _run_destroy_callbacks
     self.update_attribute(:deleted_at, Time.now) if !deleted? && persisted?
+    freeze
   end
   alias :delete :destroy
 

test/paranoia_test.rb

@@ -37,6 +37,7 @@ class ParanoiaTest < Test::Unit::TestCase
     model.delete
 
     assert_equal true, model.deleted_at.nil?
+    assert model.frozen?
     
     assert_equal 0, model.class.count
     assert_equal 0, model.class.unscoped.count
@@ -50,6 +51,7 @@ class ParanoiaTest < Test::Unit::TestCase
     model.delete
 
     assert_equal false, model.deleted_at.nil?
+    assert model.frozen?
 
     assert_equal 0, model.class.count
     assert_equal 1, model.class.unscoped.count