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

@@ -1,23 +1,18 @@
 Security Component
 ==================
 
-Security provides an infrastructure for sophisticated authorization systems,
-which makes it possible to easily separate the actual authorization logic from
-so called user providers that hold the users credentials. It is inspired by
-the Java Spring framework.
+The Security component provides a complete security system for your web
+application. It ships with facilities for authenticating using HTTP basic or
+digest authentication, interactive form login or X.509 certificate login, but
+also allows you to implement your own authentication strategies. Furthermore,
+the component provides ways to authorize authenticated users based on their
+roles, and it contains an advanced ACL system.
 
 Resources
 ---------
 
-Documentation:
-
-https://symfony.com/doc/2.7/book/security.html
-
-Tests
------
-
-You can run the unit tests with the following command:
-
-    $ cd path/to/Symfony/Component/Security/
-    $ composer install
-    $ phpunit
+  * [Documentation](https://symfony.com/doc/current/components/security/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)