Remove SSLv3 from nginx

The default enables SSLv3.

https://github.com/jfryman/puppet-nginx/blob/v0.0.9/manifests/resource/vhost.pp#L53-L54

This is no longer a sensible default: SSLv3 is ancient and now has a
published vulnerability in the design.

http://googleonlinesecurity.blogspot.co.uk/2014/10/this-poodle-bites-exploiting-ssl-30.html

By doing this, we prevent people running IE6 on WinXP lower than SP3
from accessing our service. Unfortunately, security concerns mean that
we need to make this change.