feed in fixed quantile bins and sort datapoints accordingly

[RyanK0902]

To do this, we need to determine the dependency of quantile building and sorting. If they're modularized, just identify input/output. Otherwise, determine how values are accessed.

Test Cases:

1. verify fixed bin_values --> make sure each iteration isn't rerunning weighted_quantile_sketch.
2. compare original histogram results (this runs weighted_quantile_sketch) AND quantiles built with same bins as input.