Twig + Silex

Some more WIP stuff.

I've been experimenting with using [Silex](http://silex.sensiolabs.org/) for routing and [Twig](http://twig.sensiolabs.org/) as a Template Engine for rendering our pages. The motivation behind this is the separations of logic and content in our code.

I think a template langauge such as Twig makes the pages' code much better readable. So far, I converted all pages except `Community`, and the LSP of course.

Feel free to [browse](https://github.com/LMMS/lmms.io/tree/twig) through the code and share your thoughts. But please don't look at `index.php` yet, it looks horrible :)