[stdlib] Add guard traits

The check for `array` or `Traversable` code is littered throughout the framework.  This is a prime opportunity for a trait.  Included a couple extra traits for good measure.

For example, https://github.com/zendframework/zf2/blob/master/library/Zend/Form/Fieldset.php#L297 could be:

```php
class Fieldset extends Element implements FieldsetInterface
{
    use \Zend\Stdlib\Guard\ArrayOrTraversableGuardTrait;

    // ...

    public function setMessages($messages)
    {
        $this->guardForArrayOrTraversable(
            $messages, 'Messages', __NAMESPACE__ . '\Exception\InvalidArgumentException'
        );

        foreach ($messages as $elementName => $elementMessages) {
            $this->get($elementName)->setMessages($elementMessages);
        }

        return $this;
    }
    
    // ...

}
```

Please see http://verraes.net/2013/09/extract-till-you-drop/