title: rails 3, how add a simple confirmation dialog when user clicks a link
body: <p>what is the easiest way in rails 3 to to ask "Are you sure you want to do that?" when the user clicks on a link?</p>
  
  <p>the link in this case overwrites some data with a new value. It's a simple link_to (GET) back to the same controller method, with a param[] added.</p>