Provide an integration with Twig_Util_DeprecationCollector to report deprecated Twig features.

[moufmouf]

Reported by @stof at #17:

does Mouf support reporting deprecations using the convention introduced in symfony (i.e. @trigger_error('...', E_USER_DEPRECATED), so that error handlers not supporting the convention don't convert the deprecation warning to an exception thus breaking things) ?
If no, you should probably provide an integration of the Twig_Util_DeprecationCollector, to find usage of deprecated Twig features