Generating the report in the same step resulted in the report exit code
overriding the exit code of the test runner.

The logs clutter up the test output way too much.

CI was building the image twice: once with dev dependencies and again
without. Separating the pipenv command into separate layers allows the
second build in CI to take advantage of the cache for the base
dependencies that it will share across both builds.

Install numpy along with the dev dependencies within the container.
Previously it was installed in CI only, but this meant extra work for
those running tests locally.

Install numpy to the correct site.

The branch needs the fixes from #94 to make the tests pass.