Validates if the given input is a cnpj.
Valid values:
validator.cnpj().validate('36.310.327/0001-07');
validator.cnpj().validate('38175021000110');
Invalid values:
validator.cnpj().validate('00000000000000');
validator.cnpj().validate('99999999999999');
validator.cnpj().validate('12345678900123');
validator.cnpj().validate('foo');