Improve serializers:

* Many nested levels of associations can now insert
  their information alongside the original when
  embed :ids, :include => true is true
* Add support for passing options to serializers
* Fix Array serializers so they don't try to insert
  roots for each child object and so they can be
  provided a root.
* TODO: Array serializers should require a root
* TODO: Make merging associations at the root more
  efficient if possible

test/test_helper.rb

@@ -1,7 +1,5 @@
 require "rubygems"
-require "bundler"
-
-Bundler.setup
+require "bundler/setup"
 
 require "active_model_serializers"
 require "active_support/json"