Merge pull request #25 from johnny-miyake/master

Update README.md
Add structure - extract methods to modules
remove unneeded :if condition in the #next_item and #previous_item methods
Extracted out callbacks to its own module
Extracted :helper and clean up configurable
rename :configuration reader to orderable_config
WIP - extract out configuration and orderable_class
Major Commit - Add support for multiple columns, minor other fixes
Major Commit:
* Cleanup main orderable.rb
* Eliminated the configurable module
* Generate dynamic #move_to, #list, #insert based on column
* Minor fixes, etc.
Pass column to orderable_scope_change, add :default config option
Add tests for multiple column config, remove :class_name config option, fix minor issue in listable generator
movement and other helper generater now consider :as option while naming them
updated README.md for multiple configurations
Mongoid 2 :as option fixes - aliases dont work well with criteria
update to latest rspec - use be true for #be_true expectation
Replace ruby 1.9 hash styles with old hash style
Add support for ruby 1.8 - public_send becomes #send, use class_eval for define_method, etc.
Merge pull request #26 from Bharat311/f-multi-col-support

Adds support for multiple column (backwards compatible)
Allowing numeric string to specify a target position.