refactor test models for fewer API calls

[mscarey]

It would be good if each API call was represented by just one cassette. Or at least just one in an actual test and one in conftest.

[mscarey]

I created the JSONRepository class to store mock API calls locally, and then I moved it entirely out of AuthoritySpoke, into Legislice. But I should still be able to eliminate cassettes by accessing a JSONRepository instead.