Add fluency to links helper add method

Thought it might be handy to use the links helper fluently
Rather than...
```php
$links = $this->links();
$links->add($attribs);
$links->add($otherattribs);
echo $links->get();
```

Do this

```php
echo $this->links()
               ->add($attribs)
               ->add($otherattribs)
               ->get();
```

What do you think? Seem reasonable?