feat: add support for managing nested dependencies

[z0mbix]

@gurpalw Can you please test this branch with your roles to make sure it works for you. I have tested this with the website role in ./testing/ansible/roles/website, which depends on two galaxy roles, and the local simple role, which depends on the sysctl role.

Inside the container after a converge, I now have:

# ls -1 /etc/ansible/roles/
geerlingguy.nginx
geerlingguy.redis
simple
sshd
sysctl
website

This closes issue #12

[gurpalw]

LGTM. thanks @z0mbix