Respect long namespaces for rails g scaffold

[lauratpa]

This PR changes the scaffold spec generator to take long namespaces
(longer than 2 elements) into consideration.

Fixes #1944

[benoittgt]

Build is broken on one 1.9.3

Gem::RuntimeRequirementNotMetError: rake requires Ruby version >= 2.0.0. The
current ruby version is 1.9.1.
An error occurred while installing rake (12.3.1), and Bundler
cannot continue.
Make sure that `gem install rake -v '12.3.1'` succeeds before bundling.
In Gemfile:
  rails was resolved to 3.0.20, which depends on
    railties was resolved to 3.0.20, which depends on
      rake

Can we rebuild the failing job? Is there any blocking point?

[JonRowe]

Thanks @jekuta and @benoittgt for the nudge