Basic security for cube

Hey guys :)
We liked Cube and wanted to give it a try, but since most of our app is hosted on Heroku, we didn't have the luxury of relying on firewalls for security :(

While we initially used nginx as proxy and let it handle the security, we felt that it was basic enough to roll into Cube itself (the change itself is rather small), and that it would make deployment and operations a bit easier.
It also makes it easier to "try out" Cube without thinking too much about it, which is always nice :)

There are tests for the http part (but not currently for udp), and it seems mostly ok.

TODO:
- Add tests for UDP
- Add support for SSL and WSS