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
Ansible facts aren't always enough to determine if a distro is derived
from Ubuntu or not, this is available from `/etc/os-release` when it
contains `ID_LIKE="ubuntu debian"`. This patch uses `/etc/os-release` to
correctly handle Ubuntu installations, e.g. PPA's, for all Ubuntu
derived dirtros rather than just Ubuntu itself.
