Add templating config key

Symfony 2.7-dev currently assumes this key to be set.

Author: ddeboer

Tests/Functional/Fixtures/app/config/config.yml

@@ -5,6 +5,10 @@ framework:
   test: ~
   session:
     storage_id:  session.test_storage
+  # We need to specify templating because of a bug in Symfony: 
+  # see https://github.com/symfony/symfony/issues/13710
+  templating: 
+    engines: ['php']
 
 fos_http_cache:
   cache_control: