[v2.6.2] Migration Feedback

[Sorry for multiple points in the same issue]
Migrating from (depreciated) https://github.com/mahnunchik/markerclustererplus to v2.0.4
1) **More** documentation in README please, with examples of calling each cluster algorithm & each render algorithm,
- explain differences between them
- give calling options for them.
2) Slower... seemed to be lots of re-rendering. (12,000 markers). Maybe load markers into memory, do the clustering once at each zoom level, then just render on the map as you pan close.
3) After showing/hiding markers with [marker].setVisible(), I called .render() to redraw - it just didn't work, cluster-total's were wrong, saw a cluster-total of 1 one time. Thinking about it, I needed to re-cluster, then re-render. Maybe add an example of this to the documentation as a migration point.
4) Use cdnjs (or a google version of it)
Hope this helps.