Added new columns for activities and categories:
new file:   db/migrate/20130613183820_add_columns.rb
Activities: count visited, dup status
(pending => need to be reviewed,
no => not a duplicate || original
yes => duplicate not to be displayed)

Added shoulda gem, converted the existing tests to shoulda
Added more test for activity model, to validate presence of page visited and dup status
modified:   Gemfile
modified:   app/models/activity.rb

Updated the model with the new columns
modified:   spec/models/activities_spec.rb
modified:   spec/models/categories_spec.rb
Added new tests for activities to check visited page incrementation
modified:   app/models/activity.rb
modified:   spec/controllers/activities_spec.rb
Added incrementation in controller for activity
modified:   app/controllers/activities_controller.rb
modified:   spec/controllers/activities_spec.rb