Welcome to Rails 4.
The new bundler groups.

Remove assets, add default and Rails.env.
Use exception_notification for rails 4.
Always use bundler.
Readd page caching for rails4.
Bandaid for Rails 4 routing "no all-catch" match rule.
Readd protected_attributes for rails4.
Fix validation regexp.
The json_escape monkeypatch is more a patch rather than fix.
Hope the best for utf8 and http header handling in rails4.
New (rails 3?) way of setting table name for a model.
Update gems.
Add rails-observers
Add csrf token for post-related ajax request.
Fix image upload error with local_flat image-store method.

local_flat still using some hierarchy for jpeg, preview, and sample images,
Create those folders automatically.

And remove file_hierarchy prefix for jpeg_path,
since it's not supposed to be used in local_flat
Remove whiny_nils from config as it's been removed.
Add eager_load configuration.
Remove active_record.auto_explain_threshold_in_seconds

It's been removed from rails.
New syntax for has_many condition.
Newer syntax for scoping.