Create forms/_has_many_associations shared partial
Install 'better_errors' gem
bundle update (with some cleanup)
Add 'binding_of_caller' gem (for 'better_errors')
Format and simplify
Whitespace, alignment
Comment out redundant `accepts_nested_attributes`
Simplify use of optional locals in views
Remove obsolete parameter
Use `object`/`collection`, not `model`/`models`

Use `object` and `collection` instead of inappropriately used `model` and `models`, respectively.

`model` should be used instead of the strange `klass` to store a model (which is a class).
Use `model` instead of `klass`
More intelligent 'new' links for memberships