Add testing setup for Ansible playbooks via Travis-CI

[theskumar]

• The role's syntax (are all the .yml files formatted correctly?).
• Whether the role will run through all the included tasks without failing.
• The role's idempotence (if run again, the role should not make any changes!).
• The role's success (does the role do what it should be doing?).

Reference: https://servercheck.in/blog/testing-ansible-roles-travis-ci-github