pulled out the columns and model modules into their own files, and pulled out the move_to logic into its own object
pull out pruning logic into its own module and split up complex method
pull out moving logic into its own module and break up complex methods
move rebuild into its own class and simplify code
move complex iteration methods into separate module (one of them has no tests, and it doesn't seem to behave correctly but I don't know enough about it to know for sure)
refactor complex sql conditions
move retry transaction logic into module, and moved set validation sql query into class and replaced strings with Arel.
move require statements into the file that needs them
don't need entire namespace, and include an earlier commit that got deleted by a rebase
remove ruby 1.9 hash syntax
Merge pull request #193 from shevaun/master

Refactor challenge: improve code climate score
Refactored all_roots_valid?
Extracted validator predicates to Validators module.
Moved scope_string out into its own method.
Made the responsibilities of acts_as_nested_set clear.
Remove untested, unused sorted_each_with_level.
Removed untested method sorted_nested_set_options
Rename validators to validatable and introduce rebuildable.
Added pry debugging to the Gemfile.
Simplify logic in Tree#set_left_and_rights