pred_real.m and scoring_alg_single_user.m generate same results

- Fix issues in both functions
- Error in scoring_alg where b(j) calculated incorrectly with yhat.
  Change yhat to zhat.
- Fix potential bug in pred.m where calculation of b(j) did not have
  correct parenthesis around it.
- Made both files sort data by user attempts.
- Implement effective trials ('eff_trials') in scoring_alg and change
  way xmat calculated.