title: Why AngularJS currency filter formats negative numbers with parenthesis?
body: <p><a href="http://plnkr.co/edit/yY9HfwCSAx9DdoQlkKIE?p=preview"><strong>Live Demo</strong></a></p>
  
  <p>Why this:</p>
  
  <pre><code># Controller
  $scope.price = -10;
  
  # View
  {{ price | currency }}
  </code></pre>
  
  <p>results in <code>($10.00)</code> rather than <code>-$10.00</code>?</p>