README updates from rel-tverberg
README updates from rel-tverberg

Indicated that 3.10.2.3 hotfix did not completely remove stacked
ensembles from Flow. Users can train SE models in Python and R, and
then view the SE models in Flow.

h2oai/h2o-3,h2oai/h2o-dev,spennihana/h2o-3,h2oai/h2o-3,h2oai/h2o-dev,spennihana/h2o-3,spennihana/h2o-3,mathemage/h2o-3,h2oai/h2o-3,michalkurka/h2o-3,michalkurka/h2o-3,michalkurka/h2o-3,h2oai/h2o-dev,h2oai/h2o-3,michalkurka/h2o-3,h2oai/h2o-dev,spennihana/h2o-3,spennihana/h2o-3,spennihana/h2o-3,michalkurka/h2o-3,h2oai/h2o-3,h2oai/h2o-3,h2oai/h2o-dev,mathemage/h2o-3,michalkurka/h2o-3,mathemage/h2o-3,mathemage/h2o-3,mathemage/h2o-3,michalkurka/h2o-3,h2oai/h2o-dev,h2oai/h2o-3,mathemage/h2o-3,h2oai/h2o-3,spennihana/h2o-3,mathemage/h2o-3,h2oai/h2o-dev