Binstub the generators which shellout.

Since we are binstubbing things in general, it's a good idea to actually
try them out when using the generators in the example apps.
Exclude ActiveRecord configs when not available.

More people are not using ActiveRecord these days. The generators should
not include any configs related to `ActiveRecord` when it is not
available. This allows rspec configurations to work properly out-of-the-
box for these other apps.
Include smoke task for non-ActiveRecord apps.

Creates a 2nd set of generator and smoke tasks which target an example
app which does not use ActiveRecord. In order to accomplish this, a
custom in-memory model is used which supports enough of the AR protocol
to allow default specs to pass.

Use a custom "in-memory" model as the ORM replacement. This is a simple
stand-in allowing us to continue to use all of the other Rails
generators. It also prevents us from needing to pull in another ORM gem
such as such as Mongoid, DataMapper, ROM, etc.

The custom "model" is necessary as the non-ActiveRecord example app's
specs fail with `NameError`s. This is due to the other Rails' generators
expecting to have a "model" type class available, but Rails is unable to
load it.  Just adding the classes does not work as the generated
controllers, form helpers, rendering process, etc. are so tightly
coupled to the `ActiveModel` API interface that all sorts of things
start failing.
Move example app geneators.

Change the directory name from "templates" to "example_app_generator" to
better describe what this directory holds. It is both custom Rails
templates, as well as, generator files.
Use feature checks for the rails_helper generator.

To help future proof changes in Rails, toggle on feature checks instead
of the Rails version. Use this in the specs as well.

Simplify the case where `ActiveRecord` is not available, by checking for
all options at onice instead of trying to toggle on a feature or Rails
version.
Note new behavior in Changelog.
Include acceptance smoke task for job generator.
Fix constant reference.
Merge pull request #1150 from rspec/remove-fixtures-on-no-ar

Remove `ActiveRecord` based settings from generated `rails_helper`