Added before building section to readme, to instruct users to setup the python environment and packages first
Added before building section to readme, to instruct users to setup the
python environment and packages first

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