awesome nested set implementation for Active Record

 Awesome Nested Set is an implementation of the nested set pattern for
 ActiveRecord models. It is a replacement for acts_as_nested_set and
 BetterNestedSet.
 .
 This is a new implementation of nested set based off of
 BetterNestedSet that fixes some bugs, removes tons of duplication,
 adds a few useful methods, and adds STI support.