Repository maintenance

[userCG86]

A few changes have been instituted, including:

1. reducing requirements.txt to the minimum necessary
2. fixing Joan's english
3. only allowing csv uploads
4. untracking the submissions file to get a clean leaderboard with each app launch
5. removing unused files
6. reducing the number of sample submissions
7. renaming results.csv to true_y.csv to more easily identify it
8. clean up error handling
9. adding back participant score plot