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

vendor/sebastian/environment/README.md

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+# Environment
+
+This component provides functionality that helps writing PHP code that has runtime-specific (PHP / HHVM) execution paths.
+
+[![Latest Stable Version](https://poser.pugx.org/sebastian/environment/v/stable.png)](https://packagist.org/packages/sebastian/environment)
+[![Build Status](https://travis-ci.org/sebastianbergmann/environment.png?branch=master)](https://travis-ci.org/sebastianbergmann/environment)
+
+## Installation
+
+To add Environment as a local, per-project dependency to your project, simply add a dependency on `sebastian/environment` to your project's `composer.json` file. Here is a minimal example of a `composer.json` file that just defines a dependency on Environment 1.0:
+
+    {
+        "require": {
+            "sebastian/environment": "1.0.*"
+        }
+    }
+
+## Usage
+
+```php
+<?php
+use SebastianBergmann\Environment\Runtime;
+
+$runtime = new Runtime;
+
+var_dump($runtime->getNameWithVersion());
+var_dump($runtime->getName());
+var_dump($runtime->getVersion());
+var_dump($runtime->getBinary());
+var_dump($runtime->isHHVM());
+var_dump($runtime->isPHP());
+var_dump($runtime->hasXdebug());
+var_dump($runtime->canCollectCodeCoverage());
+```
+
+### Output on PHP
+
+    $ php --version
+    PHP 5.5.8 (cli) (built: Jan  9 2014 08:33:30)
+    Copyright (c) 1997-2013 The PHP Group
+    Zend Engine v2.5.0, Copyright (c) 1998-2013 Zend Technologies
+        with Xdebug v2.2.3, Copyright (c) 2002-2013, by Derick Rethans
+
+
+    $ php example.php
+    string(9) "PHP 5.5.8"
+    string(3) "PHP"
+    string(5) "5.5.8"
+    string(14) "'/usr/bin/php'"
+    bool(false)
+    bool(true)
+    bool(true)
+    bool(true)
+
+### Output on HHVM
+
+    $ hhvm --version
+    HipHop VM 2.4.0-dev (rel)
+    Compiler: heads/master-0-ga98e57cabee7e7f0d14493ab17d5c7ab0157eb98
+    Repo schema: 8d6e69287c41c1f09bb4d327421720d1922cfc67
+
+
+    $ hhvm example.php
+    string(14) "HHVM 2.4.0-dev"
+    string(4) "HHVM"
+    string(9) "2.4.0-dev"
+    string(42) "'/usr/local/src/hhvm/hphp/hhvm/hhvm' --php"
+    bool(true)
+    bool(false)
+    bool(false)
+    bool(true)
+