Make all specs pass on rails 4.1.0.beta1

http://edgeapi.rubyonrails.org/classes/ActiveRecord/Reflection/ClassMethods.html#method-i-reflect_on_association
http://edgeapi.rubyonrails.org/classes/ActiveRecord/Associations/ClassMethods.html#method-i-has_and_belongs_to_many
https://github.com/rails/rails/blob/72bb3fc297a3548e6748867bfb55a077b7b7728c/activerecord/lib/active_record/associations.rb#L1523-L1526

More info about the has and belongs to many becomes a has many through
Make has_and_belongs_to_name_table_name  a private method