title: nightwatchJS how to use assert.containsText on a table?
body: <p>I've just starting using nightwatch and I want to confirm that a table is correctly populated.  From the terminal I can do something like:</p>
  
  <p><code>$("div#systemViewTable table tbody tr td.sortable").text()</code></p>
  
  <p>and I get a bunch of text. However when I trying the same selector in nightwatch I just get an empty string.  I.E.></p>
  
  <p><code>browser.assert.containsText("div#systemViewTable table tbody tr td.sortable", "some text")</code></p>
  
  <p>How can I make this work properly?</p>