title: Access to faces in BufferGeometry
body: <p>geometry.faces accessible only for new THREE.BoxGeometry. Then I try to use THREE.BoxBufferGeometry I can't change color for faces.</p>
  
  <p>Not working: </p>
  
  <pre><code>  var geometry = new THREE.BoxBufferGeometry( 100, 100, 100 );
    for ( var i = 0; i &lt; geometry.faces.length; i ++ ) {
      geometry.faces[ i ].color.setHex( Math.random() * 0xffffff );
    }
  </code></pre>
  
  <p>Working:</p>
  
  <pre><code>  var geometry = new THREE.BoxGeometry( 100, 100, 100 );
    for ( var i = 0; i &lt; geometry.faces.length; i ++ ) {
      geometry.faces[ i ].color.setHex( Math.random() * 0xffffff );
    }
  </code></pre>