[alpha] Addition of test suites for QA and text classification model wrapper

[NISH1001]

Changes

• tests/data/*.json data samples are used to load the data fixtures for tests
• tests/models/test_qa.py has a test suite for testing default QA wrapper
• tests/models/test_classification.py has a test suite for testing default text classification model
• pytest -m metrics can be used for only running test suite for metrics
• pytest -m models can be used for models