MAR-132: Pin packages as part of wsgi_website role test to ensure reproducability:

- Provide explicit list of packages being deployed. This should ensure
we can always reproduce the tests without being affected by new
releases of packages.
- Updated expected requirements in test for the jedi version.

MAR-132: Added support for Debian 9 (Stretch) to wsgi_website role:

- Set the shell for application system account explicitly (workaround
for Debian bug 865762 in Stretch).
- Updated Molecule tests to cover Debian 9.
- Updated Molecule test preparation playbook to account for a number
of differences between Jessie and Stretch (mainly related to mailing
functionality).
- Renamed a couple of variables in test for sending out mails to make
it clearer what is being looked up as part of regex matching.
- Updated Molecule tests where certain paths depend on what Debian
release they are ran against.
- Split-up Jessie-specific tests into separate file.
- Remove the /bin/ss utility instead of renaming it (testinfra socket
tests do not work with /bin/ss).

MAR-131: Added support for specifying Python version in wsgi_website role:

- Introduced additional role parameter for specifying the Python
version.
- Updated tests to verify new functionality.
- Fixed existing tests to account for differences between Python 2 and
Python 3 - including changes to WSGI test applications.
- Updated documentation, documenting new parameter and fixing one
minor typo.
- Updated release notes.
- Bumped default version of Gunicorn/futures used.

MAR-129: Updated wsgi_website role for Ansible 2.5.x and new Molecule:

- Include top-level linting configuration in test configuration file.
- Fixed linting errors.
- Updated Ansible deprecation warnings related to use of
state=installed with apt module.
- Updated how hosts are being referenced in tests.
- Rename the 'ss' utility in order to properly test socket
connectivity as a workaround for Testinfra bug.

MAR-128: Upgraded tests for ROLE_NAME role:

- Switch to new Molecule configuration.
- Updated set-up playbook to use become: yes.
- Moved some preparatory steps outside of the main playbook (eases
idempotence tests).
- Updated tests to reference the yml inventory file.
- Updated tests to use new fixture (host instead of individual ones).
- Switched to extracting hostname instead of hard-coding it in a
couple of tests.
- Fixed some linting issues.
- Updated one of the tests that depend on output of pip freeze due to
new versions of packages coming out.
- Updated hostname to include Debian version (for future expansion).
- Renamded some test data to match new hostname.