title: Format footer values in ui-grid
body: <p>How do I format the aggregate value for a column in ui-grid?</p>
  
  <p>With my numbers I get something horrible like </p>
  
  <pre><code>total: 6370.046074130321
  </code></pre>
  
  <p>when I would like </p>
  
  <pre><code>total: $6370.05
  </code></pre>
  
  <p>I tried both:</p>
  
  <pre><code>footerCellTemplate: '&lt;div class="ui-grid-cell-contents" &gt;{{COL_FIELD | currency}}&lt;/div&gt;',
  </code></pre>
  
  <p>and</p>
  
  <pre><code>footerCellTemplate: '&lt;div class="ui-grid-cell-contents" &gt;{{grid.getCellValue(row, col) | currency}}&lt;/div&gt;',
  </code></pre>
  
  <p>but none of them work.</p>