`progress reset` doesn't work for exercise with Q&A grading

[damithc]

A tester reported that progress reset doesn't work for some exercises. Example:

T4L1

In the "view-commits" exercise, the command gitmastery progress reset does not work

Steps to reproduce:

1. Complete the "view-commit" exercise as usual
2. Check that your answer is correct by running gitmastery verify
3. Run gitmastery progress reset in the view-commits folder
4. Open answers.txt and notice your answer should still be there

Similarly for sensors-checkout and sensors-diff. All three are graded based on Q&A, so, I'm guessing it's something to do with the Q&A grading mode.

[jovnc]

I have fixed this in this PR: git-mastery/app#38

It would require app update to take effect, as progress reset currently doesn't re-download base files (ie. answers.txt)