/**
> zip([['row0col0', 'row0col1', 'row0col2'],
       ['row1col0', 'row1col1', 'row1col2']]);

[["row0col0","row1col0"],
 ["row0col1","row1col1"],
 ["row0col2","row1col2"]]
*/
const zip = rows => rows[0].map((_,c) => rows.map(row=>row[c]))