Merge branch '1.x' into 2.x

* 1.x:
  simplified code
  use load() instead of loadTemplate() in tests
  added the possibility to pass a TemplateWrapper to Twig\Environment::load()

src/Test/IntegrationTestCase.php

@@ -200,7 +200,7 @@ abstract class IntegrationTestCase extends TestCase
                     return $prevHandler ? $prevHandler($type, $msg, $file, $line, $context) : false;
                 });
 
-                $template = $twig->loadTemplate('index.twig');
+                $template = $twig->load('index.twig');
             } catch (\Exception $e) {
                 if (false !== $exception) {
                     $message = $e->getMessage();