adding :through option to replace :nesting option and moving ResourceAuthorization class code into ControllerResource

allow access to classes when using hash conditions since you'll generally want to narrow it down with a database query

removing unauthorized! in favor of authorize! and including more information in AccessDenied exception - closes #40

renaming ActiveRecordAdditions#can method to accessible_by since it flows better and makes more sense

adding caching to current_ability class method, if you're overriding this be sure to add caching there too

adding can method to Active Record for fetching records matching a specific ability, still needs documentation

renaming :class option to :resource for load_and_authorize_resource which now supports a symbol for non models - closes #45

allow additional arguments for be_able_to matcher, this requires Ruby 1.8.7 or higher to use matcher

Adding :class option to load_resource so one can customize which class to use for the model - closes #17

Don't fetch parent of nested resource if *_id parameter is missing so it works with shallow nested routes - closes #14

Adding :collection and :new options to load_resource method so we can specify behavior of additional actions if needed.

turning load and authorize resource methods into class methods which set up the before filter so they can accept additional arguments