include quizblock_random in tests and flake8

@djredhand, lines 124 - 126 of `quizblock_random/models.py` refer to variables `set_len` and `question_set` that haven't been defined anywhere, so they would break if they ever get run. Flake8 would've told you this already if you'd run it. I commented those lines out, but they clearly need to be fixed.