[DomCrawler] Added support for slicing nodes

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | yes
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | 
| License       | MIT

There are no easy way to slice nodes in specific range. I created a method using \LimitIterator. Works fine for me.

An example using is:
```php
     $crawler->filter('h1')->slice(5, 10)->each(function ($node, $i) {
         return $node->text();
     });