Upgrade ruby version for building the dev VM

gds-boxen [1] no longer includes that version. 2.0.0 works for the version
of puppet that we use [2].

[1] https://github.com/boxen/puppet-ruby/tree/master/files/definitions
[2] https://docs.puppetlabs.com/guides/platforms.html#ruby-versions
Add Nginx status to collectd on app machines

This adds connection stats from nginx into graphite.

See:
https://collectd.org/wiki/index.php/Plugin:nginx
http://wiki.nginx.org/HttpStubStatusModule
Rearrange nginx modules to reduce hiera duplication
Merge pull request #529 from alphagov/add-nginx-status

Add nginx status
Merge pull request #528 from alphagov/bump-ruby-version

Upgrade ruby version
Fix nginx import on non app roles

App servers are not the only servers with nginx.
Merge pull request #531 from alphagov/fix-nginx-includes

Fix nginx import on non app roles
Allow redis from frontend machines

Redis sessions required by admin app which is hosted on frontend
machines, not backend machines.
Merge pull request #532 from alphagov/allow-redis-from-frontend

Allow redis from frontend machines
collectd::plugin::nginx is a class not a defined type
Merge pull request #533 from alphagov/fix-nginx-includes

collectd::plugin::nginx is a class not a defined type