-click="sortBy(null)">Set to unsorted</button>
  <hr/>
  <table class="friends">
    <tr>
      <th>
        <button ng-click="sortBy('name')">Name</button>
        <span class="sortorder" ng-show="propertyName === 'name'" ng-class="{reverse: reverse}"></span>
      </th>
      <th>
        <button ng-click="sortBy('phone')">Phone Number</button>
        <span class="sortorder" ng-show="propertyName === 'phone'" ng-class="{reverse: reverse}"></span>
      </th>
      <th>
        <button ng-click="sortBy('a