Nearly finished the reference solution

Tonight I continued working on writing the CS assignment that will be deployed to students in a few weeks. I mostly focused on writing more test cases to exercise student code on difficult cases, fixing up the reference solution in the process. The reference solution may be finished now, but it's possible that it has more tiny bugs that will be uncovered as I continue to write tests. Once that's done, I "just" need to write the documentation/instructions/writeup.