db:rollback

Hi, I wanted to rollback an application but the database was not rolled back.

What do you think about adding a `deploy:db:rollback` to this gem. This task could be also hooked after the `deploy:reverted` hook and run `rake db:rollback`

Review the existing Capistrano Rails deployment task definitions and hook wiring, then trace how deploy:reverted is handled. The requested work is complete when a deploy:db:rollback task runs rake db:rollback and can be invoked after deploy:reverted; verify it with the repository's existing task checks.

Written by the indexing model from the issue text.