Use older production settings for assets

- They were removed while upgrading to Rails 4.8.
- https://github.com/codetriage/codetriage/blob/af554ad9d059ccc277f90cc5f51e9442514dc41d/config/environments/production.rb#L11
- https://github.com/codetriage/codetriage/blob/af554ad9d059ccc277f90cc5f51e9442514dc41d/config/environments/production.rb#L14
- Added them back.