Add test_models.py. Fix some exception error types.

- Add 2 new tests for Break and WorkShift models.
Add some more test.

- Tests for SchedulingInfo, TimeWindow, Order.

- Enhanced all tests with assertions of JSON schema validators.
More tests and fixes.
100% test coverage reached; Achievement unlocked.
Apply review feedback.

- Set optimo_api's fixture scope to "module".
Add docstrings for OptimoAPI class and its methods.
Add docstrings for CoreOptimoAPI class and its methods.
Add docstrings for the custom encoders.
Add docstring to BaseModel.
Remove the Todo section from the README.md
Update setup.py

- Promote release from Pre-Alpha to Alpha status.

- Change version to 0.0.1