Update README.md

added `modules` in `puppet:///modules/apt/10periodic` uri
Update unattended_upgrade_automatic.pp

added `modules` in `puppet:///modules/apt/10periodic` uri
Update apt_unattended_upgrade_automatic_spec.rb

added `modules` in `puppet:///modules/apt/10periodic` uri
Merge pull request #13 from damusnet/patch-1

added `modules` in `puppet:///modules/apt/10periodic` uris