Constructs the ImageToolkitManager object.
\Traversable $namespaces: An object that implements \Traversable which contains the root paths keyed by the corresponding namespace to look for plugin implementations,
public function __construct(\Traversable $namespaces) {
$this->discovery = new AnnotatedClassDiscovery('ImageToolkit', $namespaces);
$this->factory = new DefaultFactory($this->discovery);
}