Update validations.js

Add doc of allowNull options property per #372.
Back-port 9a1ef08

Author: crandmck

lib/validations.js

@@ -127,9 +127,11 @@ Validatable.validatesNumericalityOf = getConfigurator('numericality');
  * ```
  *
  * @param {String} propertyName  Property name to validate.
- * @options {Object} Options
+ * @options {Object} Options See below.
  * @property {Array} inArray Property must match one of the values in the array to be valid.
- * @property {String} message Optional error message if property is not valid.   Default error message: "is not included in the list".
+ * @property {String} message Optional error message if property is not valid.
+ * Default error message: "is not included in the list".
+ * @property {Boolean} allowNull Whether null values are allowed.
  */
 Validatable.validatesInclusionOf = getConfigurator('inclusion');
 
@@ -142,6 +144,7 @@ Validatable.validatesInclusionOf = getConfigurator('inclusion');
  * @options {Object} Options
  * @property {Array} inArray Property must match one of the values in the array to be valid.
  * @property {String} message Optional error message if property is not valid.  Default error message: "is reserved".
+ * @property {Boolean} allowNull Whether null values are allowed.
  */
 Validatable.validatesExclusionOf = getConfigurator('exclusion');
 
@@ -155,6 +158,7 @@ Validatable.validatesExclusionOf = getConfigurator('exclusion');
  * @options {Object} Options
  * @property {RegExp} with Regular expression to validate format.
  * @property {String} message Optional error message if property is not valid.  Default error message: " is invalid".
+ * @property {Boolean} allowNull Whether null values are allowed.
  */
 Validatable.validatesFormatOf = getConfigurator('format');
 
@@ -176,6 +180,7 @@ Validatable.validatesFormatOf = getConfigurator('format');
  * @param {Function} validatorFn Custom validation function.
  * @options {Object} Options See below.
  * @property {String} message Optional error message if property is not valid.  Default error message: " is invalid".
+ * @property {Boolean} allowNull Whether null values are allowed.
  */
 Validatable.validate = getConfigurator('custom');
 
@@ -205,8 +210,9 @@ Validatable.validate = getConfigurator('custom');
  *```
  * @param {String} propertyName  Property name to validate.
  * @param {Function} validatorFn Custom validation function.
- * @options {Object} Options See below
+ * @options {Object} Options See below.
  * @property {String} message Optional error message if property is not valid.  Default error message: " is invalid".
+ * @property {Boolean} allowNull Whether null values are allowed.
  */
 Validatable.validateAsync = getConfigurator('custom', { async: true });
 
@@ -231,6 +237,7 @@ Validatable.validateAsync = getConfigurator('custom', { async: true });
  * @property {RegExp} with Regular expression to validate format.
  * @property {Array.<String>} scopedTo List of properties defining the scope.
  * @property {String} message Optional error message if property is not valid.  Default error message: "is not unique".
+ * @property {Boolean} allowNull Whether null values are allowed.
  */
 Validatable.validatesUniquenessOf = getConfigurator('uniqueness', { async: true });