Added property object comment to VisibilityObjectFactory (#25)

lib/VisibilityObjectFactory.js

@@ -53,6 +53,10 @@ module.exports = exports = function VisibilityObjectFactory()
  * object will include the destination object in the prototype, so that the
  * access should be transparent. This object is returned.
  *
+ * Properties are expected in the following format. Note that keywords are
+ * ignored:
+ *     { public: { prop: [ value, { keyword: true } ] } }
+ *
  * @param  {Object}   dest        destination object
  * @param  {Object}   properties  properties to copy
  * @param  {Object=}  methods     methods to copy