Graylog 0.11.0 + rbenv

Switches to using rbenv, so this can be installed without destroying other ruby applications set up on the same box, and can use a newer version of ruby than whatever happens to be default on the machine. It will also build the passenger module itself, to avoid any conflicts with other modules.

This also incorporates PRs #15, $17, #18, #19, and upgrades Graylog2 to use 0.11.0.

There are a bunch of other little improvements. You can now pick the port for mongodb and it uses `openjdk-7-jre` not `openjdk-6-jre`.

I've removed the Vagrant stuff, as it was a little alien compared to most cookbooks I've seen. It might be nice to have this cookbook embedded as a submodule in a different vagrant environment, but it shouldn't be in the main repo IMO.