fixed Twig deprecation notices

composer.json

@@ -44,7 +44,7 @@
         "symfony/twig-bridge": "~2.8|^3.0",
         "symfony/validator": "~2.8|^3.0",
         "symfony/var-dumper": "~2.8|^3.0",
-        "twig/twig": "~1.8|~2.0",
+        "twig/twig": "~1.27|~2.0",
         "doctrine/dbal": "~2.2",
         "swiftmailer/swiftmailer": "~5",
         "monolog/monolog": "^1.4.1"

src/Silex/Provider/TwigServiceProvider.php

@@ -97,8 +97,8 @@ class TwigServiceProvider implements ServiceProviderInterface
                 }
 
                 if (isset($app['form.factory'])) {
-                    $app['twig.form.engine'] = function ($app) {
-                        return new TwigRendererEngine($app['twig.form.templates']);
+                    $app['twig.form.engine'] = function ($app) use ($twig) {
+                        return new TwigRendererEngine($app['twig.form.templates'], $twig);
                     };
 
                     $app['twig.form.renderer'] = function ($app) {

tests/Silex/Tests/Provider/TwigServiceProviderTest.php

@@ -49,11 +49,11 @@ class TwigServiceProviderTest extends \PHPUnit_Framework_TestCase
             'twig.templates' => array('foo' => 'foo'),
         ));
         $loader = $this->getMockBuilder('\Twig_LoaderInterface')->getMock();
-        $loader->expects($this->never())->method('getSource');
+        $loader->expects($this->never())->method('getSourceContext');
         $app['twig.loader.filesystem'] = function ($app) use ($loader) {
             return $loader;
         };
-        $this->assertEquals('foo', $app['twig.loader']->getSource('foo'));
+        $this->assertEquals('foo', $app['twig.loader']->getSourceContext('foo')->getCode());
     }
 
     public function testHttpFoundationIntegration()