Composer and directory structure

Composer with discussed packages.
Directory structure:
- `features` - for behat scenarios
- `src` - for app logic
- `var` - for compiled templates and cache
- `web` - public directory
I completely understand @potfur's argument, and I think he is right, except for the fact that in a year those statistics will probably have changed and 5.3 will be much smaller. 
Plus, I think it is reasonable, as a policy, that we support the 3 most recent version of PHP, meaning 5.4, 5.5, 5.6. By the way, these are the officially supported versions from *The PHP Group*, which means we do not run the risk of having Vox running on potential unfixed security issues.

My real concern is not really about new features/functionalities, but rather about *security* and about establishing a *mantainable pattern for the future*, that is, we only support the 3 most recent versions of PHP, as *The PHP Group* does as well. 

Of course, I might very well be mistaken here, and I stand to review this decision at a later point in future, if necessary. But in this case, seeing as it will take about an year to have a ready product, it really seems unnecessary to me to support an old version.