Remove `ActiveRecord` based settings from generated `rails_helper`

Improve support for Rails apps which do not use `ActiveRecord`. This does not add settings in the generated `spec/rails_helper.rb` file which are specific to `ActiveRecord`. This allows new apps to run without modification, instead of raising errors.

**To Do**

- [x] Check for `ActiveRecord` in the `rails_helper.rb` template
- [x] Spec out changes to the template
- [x] Do not attempt to run migrations if the example app does not use `ActiveRecord`
- [x] Implement a 2nd set of smoke tests which do not use `ActiveRecord`
Thanks for the explanation, @cupakromer.  I was thinking the "templates" directory contained our template files for use by the generators that end users run.  Now I see that's not the case.  Maybe something like `example_app_generator` is a better name for the directory?