refactor: Use a var to determine role name to include

[stevenengland]

As the repo and role is called 'ansible' it quickly gets confusing if ones uses custom fork names or just a custom parent dir to make it more obvious what this role is for. A workaround is to substitute the role name by path.

example:

$ git clone https://github.com/paperless-ngx/ansible.git
$ mv ansible ansible_paperless_ngx
$ cd ansible_paperless_nxg
$ ansible_paperless_ngx$ molecule test

^-------- fails because the role "ansible" will not be found if the parent dir is called a more obvious way like ansible_paperless_ngx

[stevenengland]

Solved by #27