Migration to store the polymorphic attached relationship
Relationship and scope for attaching objects to slideshow
Creating uids for attached slideshows
Included a 'model with slideshow' concern
We only validate uid for not attached slideshows
Attaching slideshows to objects

Now we can assign an slideshow via a 'belongs_to' relationship
For the previous spec we need an extra migration

This migration doesn't belong to the gem migrations, it's only for testing purposes and that's because we insert it into tue dummy app migrations via the 'setup_extension' task
Removing the 'records' partial param

It must be the slideshow slides, so we don't need it
We create attached slideshows on-demand it object requires it

Instead of creating a slideshow ALWAYS when an object is created we only create the attached slideshow if a certain method returns true

We try to create it after save or every time an slideshow object is accessed
Updated Readme to attach objects to slideshows
Merge branch 'features/attach-slideshow-to-model'