Points remains in the tree after removal.

```clojure
(kdtree/nearest-neighbor (kdtree/delete (kdtree/build-tree [[0.0 0.0] [0.0 0.5] [0.0 1.0] [1.0 1.0] [1.0 0.0]] ) [0.0 0.0]) [0.0 0.0])
```
Returns #kdtree.Result{:point [0.0 0.0], :dist-squared 0.0}, but it shouldn't because the point was remove from the tree.