kmeans_visualizer.show_clusters ignore `display=False`

Using both `display=False` and `display=True` results in same thing.


It's just ugly that `kmeans_visualizer.show_clusters` display image two times.

I would prefer user to be able to use
```
visualizer.append_clusters(clusters, input_data);
# visualizer.__draw_centers(visualizer, offset, visualizer, centers, initial_centers)
# visualizer.__draw_rays(visualizer, offset, visualizer, sample, clusters, centers)
visualizer.show();
```

Not the `figure`.