Fixes /learn/, and adds a functional test to prevent regressions

Basic unit test, points to the right template.

Tests: they're good.

(This was briefly committed directly to `master` as https://github.com/18F/foia-hub/commit/cee0f88f2e929af5ce6475f119d2f15015eadc98, and then reverted in https://github.com/18F/foia-hub/commit/a6e0c392b53269b6315a01051f81e9c0a96176fe. Mea culpa.)