fixing missing globals problem in twig, closes #360

With Symfony 2.2, the globals are gone in twig theme context, so we have to pass them.

Twig Exception:
"Variable "app" does not exist in" navbar template context

references:
https://github.com/symfony/symfony/issues/3058
closes:
https://github.com/phiamo/MopaBootstrapBundle/issues/360