If the `GITHUB_TOKEN` is defined in the Ansible controller's
environment it is used to set the GitHub REST API authentication header.
This is they passed to all `uri` modules tasks which interact with the
GitHub REST API. If the `GITHUB_TOKEN` is not set, the authentication
header is not used.
Fixes#19
When used in combination with the `--skip-tags unsafe` flag the
`playbooks/UnixCLI.yaml` can be run while inside a `zsh`/`tmux` session
without it locking up due to system files going missing due to the
upgrade.
