Better handling of ENV variables in production.rb
Better handling of ENV variables in production.rb

Fixes https://github.com/spark-solutions/spark-starter-kit/issues/32

mysteryihs/guan_shu_v2,mysteryihs/guan_shu_v2,spark-solutions/spark-starter-kit,spark-solutions/spark-starter-kit,mysteryihs/guan_shu_v2,spark-solutions/spark-starter-kit