A qucik fix for https://github.com/Respect/Validation/issues/86

Fixing the issue discussed in https://github.com/Respect/Validation/issues/86 so atleast the following code gives the field names in the error messages:

    try{
        v::string()->setName('First Name')->notEmpty()->noWhitespace()->alpha()->assert($_POST['txt_first_name']);
    }catch (\Respect\Validation\Exceptions\ValidationException $e){
        echo $e->getFullMessage();
    }