Data science, second try

The structure of these tests isn't bad, but they all depend on the "production" data, which is wasteful from a time perspective, and likely to break. What I'd really prefer to see (which shouldn't be tough considering the separation of your data parser) is that for a specifically prepared sample data hash, you get the results you expected.

By doing it that way, your tests are not as fragile, and don't depend on your `JsonParser` class. Also, it means that I don't have to look at the source_data file in order to tell what the data looks like. Right now, I have no way to reason about the test data because it's in a large file on its own.