Move Aggregate#changes to class
Add pry and pry-debugger to Gemfile
Aggregate::Changes holds hash state internally
[WHITESPACE] Aggregate::Changes
Clean up Aggregate::Changes api
Extract set create or destroy keys method
Extract method to add changes on root model
Extract some more methods on Aggregate::Changes
Extract Aggregate#changes= to class
Extract handle create and destroy keys method
Aggregate#traverse_associations emits a hash

Used to emit an array; now the name of the association is the key
Reduce demeter violations :)
Extract method on applying changes to associations
Extract method on apply change to associated model
Remove before/after parms from association changes
Clean up ApplyChanges api