whole_func_string: function AssetLoader(manifest, loader) {
    this.assets = loadAssets(manifest, loader, function(err) {
      if (err) {
        console.error(err);
      }
    });
  }
func_code_string: function AssetLoader(manifest, loader) {
    this.assets = loadAssets(manifest, loader, function(err) {
      if (err) {
        console.error(err);
      }
    });
  }
func_documentation_string: Loads external assets, lets you track their progress, and lets you access the loaded data.
  @constructor