Let MaterialLoader deserialize 'attributes'.

src/loaders/MaterialLoader.js

@@ -41,6 +41,7 @@ THREE.MaterialLoader.prototype = {
 		if ( json.specular !== undefined ) material.specular.setHex( json.specular );
 		if ( json.shininess !== undefined ) material.shininess = json.shininess;
 		if ( json.uniforms !== undefined ) material.uniforms = json.uniforms;
+		if ( json.attributes !== undefined ) material.attributes = json.attributes;
 		if ( json.vertexShader !== undefined ) material.vertexShader = json.vertexShader;
 		if ( json.fragmentShader !== undefined ) material.fragmentShader = json.fragmentShader;
 		if ( json.vertexColors !== undefined ) material.vertexColors = json.vertexColors;