Use H5BP server configs

This has been tested locally but I would like to try to deploy it on digital ocean to see if it runs alright on a remote server (shouldn't be an issue)

Any feedback on this?

* * *

Checks out a stable version of h5bp/server-configs-nginx and applies it
to the /etc/nginx folder

http://goo.gl/pBfB4W

Misc:
Adds "restart nginx" handler

closes https://github.com/roots/bedrock-ansible/issues/31
Since this isn't used I'm not sure we should include it by default yet.

This should ideally be identical to https://github.com/roots/bedrock-ansible/blob/master/roles/wordpress-sites/handlers/main.yml if we kept it in. Annoying that Ansible can't call handlers from another role.