* Prep to track conditions other than just "dropped" or "kept"
* Count up instead of down
* Drop or retain whole multiplier clusters based on their first feature
* Calculate a global feature dropping sequence
* Switch over to using the drop sequence for drop-fraction
* Remove unused arguments for the old drop-fraction implementation
* Fix copy-and-paste bugs, update tests
* Properly incorporate feature_minzoom into the drop sequence, I hope
* Rename drop_by to drop_sequence
* See if sorting within clusters fixes filter stability between zooms
* Remove very chatty debug print
* Update changelog and version
* Use named constants instead of numbers for feature dropping/keeping
* Add comment to explain purpose and method of bit reversal