Replace SQLite and pickling with Python class instances; closes #37

[mileswwatkins]

@jcarbaugh, this is passing tests and functioning as expected upon some prodding of the CLI, but let me know if this architecture works. If so, I can finish building out v2 of the package once this is merged to master. (If I don't hear back from you soon, I may continue to add to this branch as a v2 develop branch.)