Required DI version should be 2.6 or grater

The minimum required version of `symfony/dependency-injection` is 2.6. This is because the incorporation of `Definition::setFactory`. In Symfony 2.5 or lower fails with: PHP Fatal error: Call to undefined method Symfony\Component\DependencyInjection\Definition::setFactory() in /srv/www/vendor/aws/aws-sdk-php-symfony/src/DependencyInjection/AwsExtension.php on line 53

Author: joksnet

composer.json

@@ -14,7 +14,7 @@
  "php": ">=5.5",
  "aws/aws-sdk-php": "^3.2.4",
  "symfony/config": "~2.3",
- "symfony/dependency-injection": "~2.3",
+ "symfony/dependency-injection": "~2.6",
  "symfony/http-kernel": "~2.3"
  },
  "require-dev": {
@@ -36,4 +36,4 @@
  "tests/fixtures"
  ]
  }
-}
+}