Address Deprecation to cache control

[JPrevost]

Mar 16 06:47:11 mit-bento app/web.1:  DEPRECATION WARNING: `config.static_cache_control` is deprecated and will be removed in Rails 5.1. 
Mar 16 06:47:11 mit-bento app/web.1:  Please use 
Mar 16 06:47:11 mit-bento app/web.1:  `config.public_file_server.headers = { 'Cache-Control' => 'public, max-age=30758400' }` 
Mar 16 06:47:11 mit-bento app/web.1:  instead. 
Mar 16 06:47:11 mit-bento app/web.1:   (called from block in <top (required)> at /app/config/environments/production.rb:29)