upgrade email system

http://wagn.org/upgrade_email_system 
http://wagn.org/convert_system_emails_to_flexmail_system
a problem: the erb code in the messages for the system mail will be escaped in a strange way when added to the db here
e.g. `href="<%= @change_url %>"` becomes `href=""<%= @change_url %">"`
Are there other solutions for this besides defining Card::Set::Right::Message with method 

```ruby
def clean_html?
  false
end
```