less sed, some tests, use dpkg for installs on debian/ubuntu

I'm submitting this pull request but the changes I've made may not suit some environments. I've removed the use of execute resources with sed to modify sshd_config and replace with the use of OpenSSH cookbook attributes. For this to work in your environment you would need to manage all ssh set-up using OpenSSH so it's a personal choice that may not suite everybody.

- use OpenSSH cookbook to set sshd_config attributes. 
- add test kitchen support with some ServerSpec tests for Ubuntu
- use the duo security packages on ubuntu/debian