I'm adding a basic test to validate that the integrals match the reference files. I used pytest because I've had good experience with it and I couldn't find a C++ testing framework that looked easy to get started with. If we want to test more fine-grained than whole program inputs and outputs we'll have to reach for something more complex though. I thought about testing all of the examples but I'm prioritizing getting something merged so we at least have some automated test. I like being able to get some feedback in a few seconds so when we expand testing I'd like an option to run all tests or just a quick one.

closes #11