Changelog
* smoother Plotly-based surface plots with exact mesh if the Voronoi graph can be boxed, or higher resolution grid-sampled surface otherwise
* new singularity container in 4 flavors (for Python 3.6, 3.7, 3.8 and 3.9) with introspection to determine which Python to use in any similar container
* bugfix in GWR for oversized `residuals` attribute
* rwa autosaving mechanism admits a callable for attribute/argument `rwa_file` to lazily create temporary files in distributed `RWAnalyzer.pipeline` execution settings
* `PipelineStage` and `RWAnalyzer.pipeline.append_stage` admit argument `run_everywhere` for stages like *fresh_start*