Bump minimal requirements

Author: jderusse

Tests/ContainerBuilderTest.php

@@ -1288,8 +1288,8 @@ public function testNoClassFromGlobalNamespaceClassIdWithLeadingSlash()
 
     public function testNoClassFromNamespaceClassIdWithLeadingSlash()
     {
-        $this->expectException('Symfony\Component\DependencyInjection\Exception\RuntimeException');
-        $this->expectExceptionMessage('The definition for "\Symfony\Component\DependencyInjection\Tests\FooClass" has no class attribute, and appears to reference a class or interface. Please specify the class attribute explicitly or remove the leading backslash by renaming the service to "Symfony\Component\DependencyInjection\Tests\FooClass" to get rid of this error.');
+        $this->expectException('Symfony\Component\DependencyInjection\Exception\InvalidArgumentException');
+        $this->expectExceptionMessage('Service definition "\Symfony\Component\DependencyInjection\Tests\FooClass" has no class, and its name looks like a FQCN but it starts with a backslash; remove the leading backslash.');
         $container = new ContainerBuilder();
 
         $container->register('\\'.FooClass::class);

composer.json

@@ -18,7 +18,7 @@
     "require": {
         "php": "^7.1.3",
         "psr/container": "^1.0",
-        "symfony/service-contracts": "^1.1.2"
+        "symfony/service-contracts": "^1.1.6"
     },
     "require-dev": {
         "symfony/yaml": "~3.4|~4.0",