Add getHydrator method to the HydratorFactory

[xico42]

Fix issue #26

Now it is possible to use the HydratorFactory as a real factory:

<?php

use GeneratedHydrator\Configuration;

require_once __DIR__ . '/vendor/autoload.php';

class Example
{
    public    $foo = 1;
    protected $bar = 2;
    protected $baz = 3;
}

$config        = new Configuration('Example');
$hydrator = $config->createFactory()->getHydrator();

var_dump($hydrator->extract($object)); // ['foo' => 1, 'bar' => 2, 'baz' => 3]
$hydrator->hydrate(
    ['foo' => 4, 'bar' => 5, 'baz' => 6],
    $object
);
var_dump($hydrator->extract($object)); // ['foo' => 4, 'bar' => 5, 'baz' => 6]

[Ocramius]

LGTM

[Ocramius]

Failure is CS/unrelated 👍