Correct type in documentation in instance save()

The type is an array of strings for the property names. Not an object.

lib/instance.js

@@ -480,7 +480,7 @@ Instance.prototype._setInclude = function(key, value, options) {
  * This error will have a property for each of the fields for which validation failed, with the error message for that field.
  *
  * @param {Object} [options]
- * @param {Object} [options.fields] An optional array of strings, representing database columns. If fields is provided, only those columns will be validated and saved.
+ * @param {string[]} [options.fields] An optional array of strings, representing database columns. If fields is provided, only those columns will be validated and saved.
  * @param {Boolean} [options.silent=false] If true, the updatedAt timestamp will not be updated.
  * @param {Boolean} [options.validate=true] If false, validations won't be run.
  * @param {Function} [options.logging=false] A function that gets executed while running the query to log the sql.