Adds "playbook", "role", and "task" fields to the output when a task fails.

This makes it easier to pinpoint where the problem is, especially
when you have a lot of roles and playbooks.

e.g.:

    failed: [vagrant] => {..."playbook": "/Users/marca/dev/ansible/vagrant.yml",
                          ..."role": "pythonapp",
                          ..."task": "pip install -r /opt/src/{{ sm_app_role }}/requirements.txt"...}