.rndSeed   - [] random seed for kmeans; useful for replicability
   .outFrac   - [0] max frac points that can be treated as outliers
   .minCl     - [1] min cluster size (smaller clusters get eliminated)
   .metric    - [] metric for pdist2
   .C0        - [] initial cluster centers for first trial

 OUTPUTS
  IDX    - [n x 1] cluster membership (see above)
  C      - [k x p] matrix of centroid locations C(j,:) = mean(X(IDX==j,:))
  d      - [1 x k] d(j) is sum of distances from X(IDX==j,:) to C(j,:)
      