Packagist is truncating `PackageLink` versions.

As a pseudo-code to reproduce the issue, try following:

```php
public function testDoesNotTruncateVersions()
{
    $version = str_repeat('>=1', 1000);
    $require = new \Packagist\WebBundle\Entity\RequireLink();

    $require->setPackageVersion($version);

    $this->entityManager->persist($require);
    $this->entityManager->flush($require);
    $this->entityManager->refresh($require);

    $this->assertSame($version, $require->getPackageVersion());
}
```

src/Packagist/WebBundle/Entity/PackageLink.php

@@ -33,7 +33,7 @@ abstract class PackageLink
     private $packageName;
 
     /**
-     * @ORM\Column()
+     * @ORM\Column(type="text")
      */
     private $packageVersion;