Update symfony2.md

Change app/config.yml to app/config/config.yml
Update symfony2.md

Small update in the doc
User/Project@SHA: symfony/symfony-standard@c3df96fceb271cf7662a27582f8bbff6b39687a8
Merge pull request #666 from ErikSaunier/patch-2

Update symfony2.md
Merge pull request #665 from ErikSaunier/patch-1

Update symfony2.md
remove package and subpackage annotations closes #519