Docstrings and Unit Tests

- [x] Adapter docstrings
- [x] Serializer docstrings
- [x] Install sinon for stub/mocking
- [x] Adapter unit tests
- [x] Serializer unit tests

/cc @holandes22 @benkonrath
I'm not even sure if the way we are calling metaForType is correct—we can discuss this further in a separate issue.