Feature/docker installation

What changed:

• Added playbook for installing docker with specific version
• Described current gitlab docker-compose.yml
• Described current ghost blog docker-compose.yml
• Described current nexus docker-compose.yml

How I can apply it:

• to apply this changes on your environment you should:

ansible-playbook -K -i environments/prod playbooks/docker.yml

How I can test it:

• Docker daemon installed
• Docker daemon enabled
• Docker daemon launched
• Role tested on local dev environment

Issues:

• #1 (closed)