message: Include `value` parameter in documentation
  This is a required parameter to validate a single field.
  People should be able to learn this from the documentation and not have to debug the source code on their own.
diff: @@ -32,7 +32,7 @@ The selector passed to the `validate` method can have the following forms:
  validator.validate();
  // validate a field that has a matching name with the provided selector.
  -validator.validate('field');
  +validator.validate('field', value);
  // validate a field within a scope.
  validator.validate('scope.field');
  