fix(attributes-to-props): undo default function parameter

Reverting the default parameter set in `attributesToProps` will
enable ES5 compatibility since this code is not transpiled.

Author: remarkablemark

lib/attributes-to-props.js

@@ -12,10 +12,11 @@ DOMProperty.injection.injectDOMPropertyConfig(
 /**
  * Makes attributes compatible with React props.
  *
- * @param  {Object} attributes - The attributes.
- * @return {Object}            - The props.
+ * @param  {Object} [attributes={}] - The attributes.
+ * @return {Object}                 - The props.
  */
-function attributesToProps(attributes = {}) {
+function attributesToProps(attributes) {
+  attributes = attributes || {};
   var props = {};
   var propertyName;
   var propertyValue;