Update to drupal 8.0.0-rc1. For more information, see https://www.drupal.org/node/2582663

vendor/symfony/routing/README.md

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+Routing Component
+=================
+
+Routing associates a request with the code that will convert it to a response.
+
+The example below demonstrates how you can set up a fully working routing
+system:
+
+```php
+use Symfony\Component\HttpFoundation\Request;
+use Symfony\Component\Routing\Matcher\UrlMatcher;
+use Symfony\Component\Routing\RequestContext;
+use Symfony\Component\Routing\RouteCollection;
+use Symfony\Component\Routing\Route;
+
+$routes = new RouteCollection();
+$routes->add('hello', new Route('/hello', array('controller' => 'foo')));
+
+$context = new RequestContext();
+
+// this is optional and can be done without a Request instance
+$context->fromRequest(Request::createFromGlobals());
+
+$matcher = new UrlMatcher($routes, $context);
+
+$parameters = $matcher->match('/hello');
+```
+
+Resources
+---------
+
+You can run the unit tests with the following command:
+
+    $ cd path/to/Symfony/Component/Routing/
+    $ composer install
+    $ phpunit