`make test` fails if `db/` has contents.

If you start the houndd server, /db becomes populated with the contents of other repos. Both jest and go test currently crawl over /db and get confused by it, usually because there are naming collisions.

I think three things would make this a little better:

1. make clean should also empty db/.
2. jest should ignore db/, which seems easy to do in a jest-config.js file.
3. go test should ignore db, which seems like we have to do manually, by using something like go test 'go list ./... | grep -v directoriesToSkip\` (I got that example from stack overflow).

A band-aid could be to just do 1 above and then run it before we run tests. That doesn't seem ideal, though, because we'd have to re-install node_modules between make clean and running the tests.