title: Assert element doesn't exist in Cucumber w/ Meteor
body: <p>I am new to Cucumber, and trying to write some simple tests to get started.  One thing I want to test is if an element is not on the page.</p>
  
  <p>In my code I do:</p>
  
  <pre><code>var myBrowser = this.browser;
  menu_data.hashes().forEach(function(menuItem, idx, items) {
    myBrowser
      .isExisting('#' + menuItem.anchor_id, function(err, isExisting) {
        if (err) {
          throw err;
        } else {
          isExisting.should.is.isfalse;
        }
      });
  });
  </code></pre>
  
  <p>Everything I have tried testing <code>isExisting</code> has failed.  I tried using <code>assert.isfalse(isExisting)</code>, but I get an error saying assert is not there.  In fact, when I try to use any methods, like <code>should.assert.toFalse(isExisting)</code> throws an error saying <code>toFalse</code> doesn't exist.</p>