support for nginx passenger debian repositories

Phusion company now provides nginx packages with precompiled [passenger support](http://blog.phusion.nl/2013/09/11/debian-and-ubuntu-packages-for-phusion-passenger/)


usage:

       class { 'nginx': 
          package_source => 'passenger',
          package_name   => 'nginx-full', # you can choose nginx-light etc.
       }

By default nginx.org repository would be used, if `package_source => ''` no apt repository would be added, so default distribution ngxinx package would be used.