Update deps & add PHPUnit Bridge

Changelogs summary:

 - symfony/phpunit-bridge installed in version v2.7.6
   Release notes: https://github.com/symfony/phpunit-bridge/releases/tag/v2.7.6

 - twig/twig updated from v1.23.0 to v1.23.1
   See changes: https://github.com/twigphp/Twig/compare/v1.23.0...v1.23.1
   Release notes: https://github.com/twigphp/Twig/releases/tag/v1.23.1

 - doctrine/inflector updated from v1.0.1 to v1.1.0
   See changes: https://github.com/doctrine/inflector/compare/v1.0.1...v1.1.0
   Release notes: https://github.com/doctrine/inflector/releases/tag/v1.1.0

 - doctrine/cache updated from v1.5.0 to v1.5.1
   See changes: https://github.com/doctrine/cache/compare/v1.5.0...v1.5.1
   Release notes: https://github.com/doctrine/cache/releases/tag/v1.5.1

 - doctrine/doctrine-cache-bundle updated from v1.0.1 to 1.2.1
   See changes: https://github.com/doctrine/DoctrineCacheBundle/compare/v1.0.1...1.2.1
   Release notes: https://github.com/doctrine/DoctrineCacheBundle/releases/tag/1.2.1

 - doctrine/doctrine-bundle updated from v1.5.2 to 1.6.0
   See changes: https://github.com/doctrine/DoctrineBundle/compare/v1.5.2...1.6.0
   Release notes: https://github.com/doctrine/DoctrineBundle/releases/tag/1.6.0

 - friendsofsymfony/user-bundle updated from dev-master to dev-master
   See changes: d5b28c3...45d6f40

composer.json

@@ -60,7 +60,8 @@
     "require-dev": {
         "doctrine/doctrine-fixtures-bundle": "~2.2.0",
         "sensio/generator-bundle": "~2.5",
-        "phpunit/phpunit": "~4.4"
+        "phpunit/phpunit": "~4.4",
+        "symfony/phpunit-bridge": "~2.7.0"
     },
     "scripts": {
         "post-install-cmd": [