TST: Migrate Shodan unit testing framework to pytest

[rmhowe425]

I am recommending that the existing unit tests be migrated away from the unittest library over to pytest.

Benefits:

• Leverage PyTest fixtures as a cleaner and simpler solution for unit testing setUp / tearDown functionality.
• pytest.mark.parameterize provides a much cleaner, simpler, and scalable method to handle multiple test cases when testing a single method.
• Easier to scope tests down to a single function, rather than testing at the class level.
• Leverage PyTest fixtures + mock requests to test HTTP requests.

[rmhowe425]

@achillean I'm also requesting your feedback on whether you're cool with me adding additional unit tests for this repo