title: alternate row style with $index binding
body: <p>I am having trouble getting an alternate-row css class applied to a knockout template with a foreach binding context.  I am using knockout 2.1 with the available <code>$index</code> context variable.</p>
  
  <p>This is whats confusing:</p>
  
  <p>My Template</p>
  
  <pre><code>&lt;li class="row" data-bind="css: { alt: $index%2 }"&gt;&lt;/li&gt;
  </code></pre>
  
  <p>results in no <code>alt</code> classes being applied, however:</p>
  
  <pre><code>&lt;li class="row" data-bind="text: $index"&gt;&lt;/li&gt;
  </code></pre>
  
  <p>works properly and displays the row number.</p>