NF: add function slice data to pull adj_matrix from 4D or 5D data brik, clean up docstrings
NF refactoring cost2thresh(2) to remove redundancy
TST: added test for slice_data
TST: added IndexError test for slice_data
NF: make_cost_thresh_lookup to genrate a lookup array holding sorted thresholds and associated absoule and rounded costs
NF: added function to for negative values in adjcency matrix, and added test