2.1.6
* Fixed rebuild! when there is a default_scope with order [Adrian Serafin]
* Testing with stable bundler, ruby 2.0, MySQL and PostgreSQL [Philip Arndt]
* Optimized move_to for large trees [ericsmith66]

2.1.5
* Worked around issues where AR#association wasn't present on Rails 3.0.x. [Philip Arndt]
* Adds option 'order_column' which defaults to 'left_column_name'. [gudata]
* Added moving with order functionality. [Sytse Sijbrandij]
* Use tablename in all select queries. [Mikhail Dieterle]
* Made sure all descendants' depths are updated when moving parent, not just immediate child. [Phil Thompson]
* Add documentation of the callbacks. [Tobias Maier]

2.1.4
* nested_set_options accept both Class & AR Relation. [Semyon Perepelitsa]
* Reduce the number of queries triggered by the canonical usage of `i.level` in the `nested_set` helpers. [thedarkone]
* Specifically require active_record [Bogdan Gusiev]
* compute_level now checks for a non nil association target. [Joel Nimety]

2.1.3
* Update child depth when parent node is moved. [Amanda Wagener]
* Added move_to_child_with_index. [Ben Zhang]
* Optimised self_and_descendants for when there's an index on lft. [Mark Torrance]
* Added support for an unsaved record to return the right 'root'. [Philip Arndt]

2.1.2
* Fixed regressions introduced. [Philip Arndt]

2.1.1
* Added 'depth' which indicates how many levels deep the node is.
  This only works when you have a column called 'depth' in your table,
  otherwise it doesn't set itself. [Philip Arndt]
* Rails 3.2 support added. [Gabriel Sobrinho]
* Oracle compatibility added. [Pikender Sharma]
* Adding row locking to deletion, locking source of pivot values, and adding retry on collisions. [Markus J. Q. Roberts]
* Added method and helper for sorting children by column. [bluegod]
* Fixed .all_roots_valid? to work with Postgres. [Joshua Clayton]
* Made compatible with polymorphic belongs_to. [Graham Randall]
* Added in the association callbacks to the children :has_many association. [Michael Deering]
* Modified helper to allow using array of objects as argument. [Rahmat Budiharso]
* Fixed cases where we were calling attr_protected. [Jacob Swanner]
* Fixed nil cases involving lft and rgt. [Stuart Coyle] and [Patrick Morgan]

2.0.2
* Fixed deprecation warning under Rails 3.1 [Philip Arndt]
* Converted Test::Unit matchers to RSpec. [Uģis Ozols]
* Added inverse_of to associations to improve performance rendering trees. [Sergio Cambra]
* Added row locking and fixed some race conditions. [Markus J. Q. Roberts]

2.0.1
* Fixed a bug with move_to not using nested_set_scope [Andreas Sekine]

2.0.0.pre
* Expect Rails 3
* Changed how callbacks work. Returning false in a before_move action does not block save operations. Use a validation or exception in the callback if you need that.
* Switched to RSpec
* Remove use of Comparable