Use JSONTestSuite to test our parser functionality

[joeslice]

As discussed in https://seriot.ch/projects/parsing_json.html, striving to be a good JSON parser involves being aware of and correctly handling certain specific data edge cases.

The scope of this ticket is to:

• embed well-defined edge case test documents from nst/JSONTestSuite
• build unit test functionality to utilize these tests documents, asserting that the correct parsing behavior is observed
• build a repeatable process for updating test documents
• document these mechanisms for update and test
• define process for reporting and handling errors, tracking remaining known issues and working towards all passing tests

[dmarcotte]

Implemented in #26 (really happy with how the infrastructure for this turned out)