Support for silex 2.0-dev

as requested PR to develop branch with addionals
well currently 2.0 version of silex is not stable, but my projects are in development as well, i just want to develop my project further while using newest version of silex. Also the old silex provider require mustache 2.1 which does not contains Cascading Filesystem Loader. 

the problem is, silex 2.0 is not backward compatible to silex 1.x at somepoint i have to break the backward compability