Add environment_vars config

[syndbg]

Adds environment_vars config.

Why

This is very much needed when using an inventory source script such as ec2.py, proxmox.py and similar since you have to pass your authentication credentials via environment variables and/or files. Files are obviously not sufficient enough for dynamic test suites.

So with this change usage is

provisioner:
  name: ansible_push
  extra_vars:
    FOO: bar

Anything other than a Hash will be marked as invalid configuration. E.g

provisioner:
  name: ansible_push
  extra_vars: []

Also changed

Bumped version to minor version 0.10.0, since we're introducing new functionality.

@ahelal

[ahelal]

Hi @syndbg,
thank you for the PR, I am currently with limited internet. I will have a look in mid Jan.

Happy new year 🎆

[ahelal]

Hi i @syndbg,
Sorry for the delay can you rebase the pr ? so i can merge

[syndbg]

@ahelal Yes, sure. Rebased.

Also noticed that I didn't add any documentation about the existence of environment_vars. Added in bbd5f88

Imo it's good to merge.

[syndbg]

Ping @ahelal :)