Fix module declaration for cucumber step generator

Fixes error message: "[WARNING] Could not load generator "rails/generators/fabrication/cucumber_steps/cucumber_steps_generator". Error: uninitialized constant Fabrication." when running `rails generate fabrication:cucumber_steps` on Ruby 2.0.0p195, Rails 3.2.13, OS X 10.8.4

See also: pull request #88
Merge pull request #164 from elizabrock/patch-1

Fix module declaration for cucumber step generator