Newest release of delayed_job_active_record breaks loading of delayed_job_groups_plugin

[hoenth]

In version 4.15 of delayed_job_active_record, they have removed loading the Configure and Job classes until after initialization (collectiveidea/delayed_job_active_record#172).

This means that the Job class is not loaded with delayed_job_groups_plugin tries to access it on line 14 of lib/delayed_job_groups_plugin.rb.

Other related libraries have encountered the same issue, such as delayed_cron_job (codez/delayed_cron_job#27).

Seems we could follow the same pattern as delayed_cron_job and check for defined?(Rails::Railtie) and if so, require a railtie file that waits until after initialization to Delayed::Backend::ActiveRecord::Job.send(:include, Delayed::JobGroups::JobExtensions)

If that makes sense, I am happy to work on it and issue a PR

[will89]

Fixed with #18.