Write usage documentation

[arBmind]

This role set is quite verbose.
Please write some common usage examples.

[arBmind]

#1 might contain a good reference

[andrzejwp]

Unfortunately #1 is incomplete, the minimum to run it is

- role: domain/create
    libvirt_domain_name: "example"
    libvirt_ssh_port: 37331
    libvirt_domain_groups: ['example']
    libvirt_base_image: "{{ ansible_local.libvirt.facts.ubuntu_cloud_image_path }}"

after previously sucessfully applying the images/ubuntu-cloud role.

Complete working playbook:

- hosts: libvirt-server
  sudo: true

  roles:

  - role: images/ubuntu-cloud
    libvirt_images_ubuntu_cloud_image_url: "https://cloud-images.ubuntu.com/trusty/20160119/trusty-server-cloudimg-amd64-disk1.img"
  - role: domain/list
  - role: domain/create
    libvirt_domain_name: "example"
    libvirt_ssh_port: 37331
    libvirt_domain_groups: ['example']
    libvirt_base_image: "{{ ansible_local.libvirt.facts.ubuntu_cloud_image_path }}"

Also, please beware of the groups syntax issue, fixed in pr #6