Integrate Pytest into automated testing

Summary

Establish a code development procedure for automated testing using Pytest.
Motivation and context

This procedure will be demonstrated by building a tests for Crossfeed API endpoint validation. Additionally a documented process will be provided to incorporate automated test in python for future code deployments.
Implementation notes

Add Pytest to environment build
Create simple pass/fail test using api endpoint mock objects.
Document a procedure for future requirements for code updates.
Document any recognized fixtures for repeatable object sets.
Document any implementation steps for future development.

Acceptance criteria

Initial API test passes/fails as expected
PyTest is integrated in Crossfeed build
Documentation is completed on procedure and implementation steps.
Pull Request merged with 'master'