Added license header for App class
Added NotFound controller, changed fallback to root_controller

In order to distinguish between the root URI (/) and a 404, a new
default NotFound controller is introduced. The root controller is called
upon requesting /, the NotFound controller in any case the router
doesn't find the requested URI.
Added require-dev section

Changed sauce's version to use dev-master when supplying --dev to
composer.
Merge branch 'master' of github.com:Brainsware/bacon