lib/assets/asset-loader.js
function AssetLoader(manifest, loader) {
  this.assets = loadAssets(manifest, loader, function(err) {
    if (err) {
      console.error(err);
    }
  });
}
function AssetLoader(manifest, loader) {
  this.assets = loadAssets(manifest, loader, function(err) {
    if (err) {
      console.error(err);
    }
  });
}
Loads external assets, lets you track their progress, and lets you access the loaded data.
@constructor