title: THREE.DragControls is not a constructor error
body: <p>I am trying to use Three.DragControls constructor for my application in three.js.
  I run npm install and npm install three-dragcontrols, receiving the message the dependency was added to the package.
  When i am trying to use new Three.DragControls i receive the error:
  "THREE.DragControls is not a constructor"</p>
  
  <p>The code: </p>
  
  <pre><code>var scene = new THREE.Scene();
  scene.background = new THREE.Color( 0xf0f0f0 );
  var camera = new THREE.PerspectiveCamera( 70, window.innerWidth / window.innerHeight, 1, 10000 );
  var objects = [];
  
  var renderer = new THREE.WebGLRenderer();
  renderer.setSize( window.innerWidth, window.innerHeight );
  document.body.appendChild( renderer.domElement );
  
  camera.position.z = 1000;
  
  var startColor;
  
  function init() {
      scene.add( new THREE.AmbientLight( 0x0f0f0f ) );
  
      var light = new THREE.SpotLight( 0xffffff, 1.5 );
      light.position.set( 0, 500, 2000 );
  
      scene.add(light);
  
      var geometry = new THREE.BoxGeometry( 40, 40, 40 );
      var geometry = new THREE.SphereGeometry( 40, 40, 40 );
  
      for (var i = 0; i &lt; 100; i++) {
          var object = new THREE.Mesh( geometry, new THREE.MeshLambertMaterial( { color: Math.random() * 0xffffff } ) );
  
          object.position.x = Math.random() * 1000 - 500;
          object.position.y = Math.random() * 600 - 300;
          object.position.z = Math.random() * 800 - 400;
  
          object.castShadow = true;
          object.receiveShadow = true;
  
          scene.add( object );
  
          objects.push( object );
      }
  
      var controls = new THREE.DragControls( objects, camera, renderer.domElement );
      controls.addEventListener( 'dragstart', dragStartCallback );
      controls.addEventListener( 'dragend', dragendCallback );
  }
  
  function dragStartCallback(event) {
      startColor = event.object.material.color.getHex();
      event.object.material.color.setHex(0x000000);
  }
  
  function dragendCallback(event) {
      event.object.material.color.setHex(startColor);
  }
  
  function animate() {
      requestAnimationFrame( animate );
  
      renderer.render(scene, camera);
  };
  
  init();
  animate();
  </code></pre>