Upgrade instructions for gem version 4.0

capistrano-postgresql gem version 4 introduces some breaking changes.

If you have gem version 3 or below, following the below upgrade steps is recommended.

• bump the gem version locally
  

    gem 'capistrano-postgresql', '~> 4.0.0'
  

  then do $ bundle install

• run the upgrade task
  This step will create the "archetype database.yml file":

    $ bundle exec cap production postgresql:upgrade4
  

• run the setup task
  

    $ bundle exec cap production setup
  

That's all!