JavaScript test runner

## Summary

Provides a `Makefile` for running JavaScript tests either individually (per assignment) or as a full suite (all assignments) for CI.

## API

Run all tests:

    % make testall

Run a specific test

    % make test ASSIGNMENT=allergies

## CI

I have not hooked this up to the `.travis.yml` file since some tests fail with `make testall` given some assignments do not follow a consistent directory/file naming convention. I will address that separately.