Make testing suite faster and more self-contained

[jvfe]

Currently, the tests are slow to run and could use some improvements, such as being more self-contained and less reliant on external data services, to account for situations such as the reconciliation services being loaded.

For this, csv-reconcile seems like a promising solution, since it would allow us to spin up our own reconciliation service inside a pytest fixture.

Idea by @gitonthescene on #12