tener('iron-form-presubmit', function() {
      this.request.method = 'put';
      this.request.params = someCustomParams;
    });

  Example of bypassing the build-in form submission:

    form.addEventListener('iron-form-presubmit', function(event) {
      event.preventDefault();
      var firebase = new Firebase(form.getAttribute('action'));
      firebase.set(form.serialize());
    });

@demo demo/index.html
*/
  Polymer({

    is: 'iron-form',

    extends: 'form',

    properties: {
      /**
       *