title: knockout.js change visible status based on if array is empty or not
body: <p>I want to be able to have a table show only if there are items in an array. I have simplified down my needs to this <a href="http://jsfiddle.net/WLapt/1/">jsfiddle</a> example.</p>
  
  <p>JS:</p>
  
  <pre><code>var view_model = {
      lines: ko.observableArray([
          {
          content: 'one'},
      {
          content: 'two'},
      {
          content: 'three'},
      {
          content: 'four'},
          ]),
      remove: function(data) {
          view_model.lines.remove(data);
      }
  };
  
  ko.applyBindings(view_model);
  </code></pre>
  
  <p>HTML:</p>
  
  <pre><code>&lt;span data-bind="visible:lines"&gt;Lines Exist&lt;/span&gt; 
  &lt;ul data-bind='foreach:lines'&gt;
      &lt;li&gt;
          &lt;button data-bind="click:$parent.remove"&gt;
              Remove
          &lt;/button&gt;
          &lt;span data-bind="text:content"&gt;&lt;/span&gt;
      &lt;/li&gt;
  &lt;/ul&gt;
  </code></pre>
  
  <p>Basically I have a web app where lines can be removed from table. If <code>array.length == 0</code>, I want to hide the entire table.</p>