Merge branch '2.3' into 2.7

* 2.3:
  Updated all the README files
  [TwigBundle] Fix failing test on appveyor
  [FrameworkBundle] Fix a regression in handling absolute and namespaced template paths
  Allow to normalize \Traversable
  Remove _path from query parameters when fragment is a subrequest and request attributes are already set Added tests for _path removal in FragmentListener
  Simplified everything
  Added a test
  Fixed the problem in an easier way
  Fixed a syntax issue
  Improved the error message when a template is not found
  [CodingStandards] Conformed to coding standards
  [TwigBundle] fixed Include file locations in "Template could not be found" exception

Author: fabpot

README.md

@@ -1,21 +1,13 @@
 Yaml Component
 ==============
 
-YAML implements most of the YAML 1.2 specification.
-
-```php
-use Symfony\Component\Yaml\Yaml;
-
-$array = Yaml::parse(file_get_contents(filename));
-
-print Yaml::dump($array);
-```
+The Yaml component loads and dumps YAML files.
 
 Resources
 ---------
 
-You can run the unit tests with the following command:
-
-    $ cd path/to/Symfony/Component/Yaml/
-    $ composer install
-    $ phpunit
+  * [Documentation](https://symfony.com/doc/current/components/yaml/index.html)
+  * [Contributing](https://symfony.com/doc/current/contributing/index.html)
+  * [Report issues](https://github.com/symfony/symfony/issues) and
+    [send Pull Requests](https://github.com/symfony/symfony/pulls)
+    in the [main Symfony repository](https://github.com/symfony/symfony)