Added tests for cli.py

Hello everyone,

hope you are all doing well!

Description

I have added unit testing for cli.py. I tried my best to make the unit tests as well-scoped as possible. This approach is slow, but I prefer it because it makes tests easy to read and it makes points of failure very easy to spot.

I took the liberty of creating an incorrect version of our test yaml file called incorrect_test_config.py under our tests/data folder. This way we can ensure that JobFunnel is behaving how it's supposed to when given incorrect data in a configuration file. Hopefully this change makes sense.

Context of change

Please add options that are relevant and mark any boxes that apply.

[ ] Software (software that runs on the PC)
[ ] Library (library that runs on the PC)
[ ] Tool (tool that assists coding development)
[x] Other

Type of change

Please mark any boxes that apply.

[ ] Bug fix (non-breaking change which fixes an issue)
[ ] New feature (non-breaking change which adds functionality)
[ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
[ ] This change requires a documentation update

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce. Please also list any relevant details for your test configuration.

[x] Tested the test_cli.py module in isolation on Ubuntu 20.
[x] Tested the entire test suite as a whole

Checklist:

Please mark any boxes that have been completed.

[x] I have performed a self-review of my own code.
[x] I have commented my code, particularly in hard-to-understand areas.
[x] I have made corresponding changes to the documentation.
[x] My changes generate no new warnings.
[x] I have added tests that prove my fix is effective or that my feature works.
[x] New and existing unit tests pass locally with my changes.
[x] Any dependent changes have been merged and published in downstream modules.

PaulMcInnis / JobFunnel