not a string.

  * A new module (ActiveSupport::Autoload) is provide that extends
    autoloading with new behavior.
  * All autoloads in modules that have extended ActiveSupport::Autoload
    will be eagerly required in threadsafe environments
  * Autoloads can optionally leave off the path if the path is the same
    as full_constant_name.underscore
  * It is possible to specify that a group of autoloads live under an
    additional path. For instance, all of ActionDispatch's middlewares
    are ActionDispatch::MiddlewareName, but they live under 
    "action_dispatch/middlewares/middleware_name"
  * It is possible to specify that a group of autoloads are all found
    at the same path. For instance, a number of exceptions might all
    be declared there.
  * One consequence of this is that testing-related constants are not
    autoloaded. To get the testing helpers for a given component,
    require "component_name/test_case". For instance, "action_controller/test_case".
  * test_help.rb, which is automatically required by a Rails application's
    test helper, requires the test_case.rb for all active components, so
    this change will not be disruptive in existing or new applications.

This commit breaks all exception catching plugins like ExceptionNotifier. These plugins should be rewritten as middleware instead overriding Controller#rescue_action_in_public.

  * Rails actions are now Rack endpoints, and can be retrieved
    via FooController.action(name) and called with an env
  * Updated some tests that relied on the old internal
    #process/#call implementation

Deprecate template, session, assigns, and layout accessors on response object. Instead access them through the controller instance. This mainly affects functional test assertions.

  ActionView::Template is now completely independent from template
  storage, which allows different back ends such as the database.
  ActionView::Template's only responsibility is to take in the
  template source (passed in from ActionView::Path), compile it,
  and render it.

Inherit TestSession from Session::AbstractStore and add indifferent access to Session::AbstractStore. 

Build query string and POST params parser on top of Rack::Request. Also switch our multipart parser to use Racks. Moved XML, JSON, and YAML parsers into ActionController::ParamsParser middleware [#1661 state:resolved]

Memoize request accessors on the Rack env so other request objects have access to the same cache [#1668 state:resolved]