Add CoreOS support

Description

CoreOS does not have any package manager and Python has to be installed manually. Calling @tziol for help with picking a better solution.

Proposal

The most common solution for CoreOS is defunctzombie/ansible-coreos-bootstrap role. It uses pypy from bitbucket tar.gz archive and the same method can be used by our OS agnostic role.

Questions

1. Should all supported OS'es use pypy or just CoreOS (leave Ubuntu using apt)?

2. CoreOS filesystem is mostly readonly and the only one writable directory in $PATH variable is /opt/bin. Should ansible_python_interpreter variable value also be OS specific (how? set manually?)?

Additional information

grep "DISTRIB_ID" /etc/*-release | cut -f 2 --delimiter="="

Ubuntu

Ubuntu

CoreOS

"Container Linux by CoreOS"

---

echo $PATH

Ubuntu

/home/ubuntu/bin:/home/ubuntu/.local/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/snap/bin

CoreOS

/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/opt/bin