Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Conflicts:
	spec/features/issues_spec.rb
	spec/models/forked_project_link_spec.rb
	spec/models/hooks/service_hook_spec.rb
	spec/models/hooks/web_hook_spec.rb
	spec/models/project_services/hipchat_service_spec.rb
	spec/requests/api/project_members_spec.rb
	spec/requests/api/projects_spec.rb
	spec/requests/api/system_hooks_spec.rb
	spec/services/archive_repository_service_spec.rb
	spec/support/matchers.rb
	spec/tasks/gitlab/backup_rake_spec.rb

These fixes were performed automatically by Rubocop's `-a` flag.

We only want them shortened by the filter, which calls to_s

Now there is a single source of information for which attribute a model
uses to be referenced, and its special character.