fuel/core — pull request #1536 by hackoh (2013-09-30 08:42:51+00:00)
Title: Add a shortcut for getting error message of validation

This function is a shortcut to getting the error message.
This is used in the following cases.

```php
add_field('from', 'from', 'required|valid_date');
$val->add_field('to', 'to', 'required|valid_date');

if ( ! $val->run())
{
$this->response(array(
'result' => 400,
'error_messages' => $val->error_message()
));
}
else
{
// validated..
}
}
}
```