Update validations.js

Add doc of allowNull options property per #372.

Author: crandmck

lib/validations.js

@@ -129,9 +129,11 @@ 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');
 
@@ -144,6 +146,7 @@ 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');
 
@@ -157,6 +160,7 @@ 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');
 
@@ -178,6 +182,7 @@ 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');
 
@@ -209,6 +214,7 @@ Validatable.validate = getConfigurator('custom');
  * @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.validateAsync = getConfigurator('custom', {async: true});
 
@@ -233,6 +239,7 @@ 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});