title: Three.JS Model exported from editor, bump map not rendering
body: <p>I have a model with a bump map.  It displays great in the three.js <a href="http://threejs.org/editor" rel="nofollow">editor</a>, but when I export the scene and load it into a scene, the model displays without the bump map. It's puzzling because the envMap and specularMap are loading just fine, but no bump map.  Any ideas?</p>
  
  <p>The exported json is here: <a href="https://www.dropbox.com/sh/xj8plnceoce1gwh/AABWChVTw6TW2hPXr5a3t9Tpa/Backpack_3_scene.json?dl=0" rel="nofollow">https://www.dropbox.com/sh/xj8plnceoce1gwh/AABWChVTw6TW2hPXr5a3t9Tpa/Backpack_3_scene.json?dl=0</a></p>
  
  <p>Here is my code for loading the exported json:</p>
  
  <pre><code>// scene
  
    scene = new THREE.Scene();
  
    // model
  
    var onProgress = function ( xhr ) {
      if ( xhr.lengthComputable ) {
        var percentComplete = xhr.loaded / xhr.total * 100;
        console.log( Math.round(percentComplete, 2) + '% downloaded' );
      }
    };
  
    var onError = function ( xhr ) {
  
    };
  
    var loader = new THREE.ObjectLoader();
  
    loader.load(model_json, function(json_scene) {
      scene.add(json_scene);
      render();
    }, onProgress, onError);
  </code></pre>