restarting ssh server handler).

- Move the SSH server installation and startup tasks to pre_tasks (the role modifies the sshd config, so it needs to be there).

# Conflicts:
#	README.rst
#	defaults/main.yml
#	handlers/main.yml
#	molecule.yml
#	tasks/main.yml
#	tests/playbook.yml
#	vars/main.yml

- Caching the entire virtualenv in Travis CI has proven to cause issues, caching just pip's cache directory.

- Use privileged container instead of just adding the sys_admin capability (the latter has been shown to be cause unrelated issues).

- Remove mention of tests/requirements.yml from the Requirements section in the README, relevant only for testing.

accordingly.

# Conflicts:
#	meta/main.yml
#	molecule.yml
#	tasks/main.yml
#	tests/playbook.yml

- Add pre-commit check for out-of-date dependencies.
- Add flake8 pre-commit check.
- List roles needed for testing (bootstraping) at
tests/requirements.yml, leave other dependencies at meta/main.yml.
- Update molecule.yml, ansible.cfg for newer versions of Molecule.
- Update documentation, playbook accordingly.