Pass only purely numeric points to kmeans module

This fixes the case where None values could potentially be passed to kmeans methods. kmeans is known to only work on purely numeric data so any non-numeric points are filtered out for kmeans interactions then added back in to the list before returning results.

Signed-off-by: Don Naegely <naegelyd@gmail.com>
Filtering the points twice is wasteful. Leave the original `for` loop on `points` and add a condition to check whether `None` is in `x['values']` and append to the `null_points` list.