title: Add confirm: "Sure?" to f.submit
body: <p>I have a form with a <code>submit_tag</code>.</p>
  
  <p>I want both to set the content value and have a js popup confirming the intent.</p>
  
  <p>I've tried <a href="https://stackoverflow.com/questions/15771582/rails-how-to-put-a-confirmation-popup-on-a-f-submit/15771639#comment31865377_15771639">the suggestion in this answer</a> and <a href="http://api.rubyonrails.org/classes/ActionView/Helpers/FormTagHelper.html#method-i-submit_tag" rel="nofollow noreferrer">what the docs describe</a>.</p>
  
  <p>Neither of the below invoke the confirmation dialog, but it does for a <code>link_to</code> tag. What am I doing wrong?</p>
  
  <pre><code>f.submit "Do this", data: {confirm: 'Are you sure?'}  
  f.submit "Do this", confirm: 'Are you sure?'
  f.submit confirm: 'Are you sure?'
  </code></pre>