Improvements in registration specs

Check for true and not truthy in registration model spec.
Cover general cases in conf registration controller.
Add test for flash in new action when ichain is set and user is not signed in.

spec/features/conference_registration_spec.rb

@@ -41,7 +41,7 @@ feature Registration do
           click_link 'Unregister'
           expect(conference.user_registered?(participant)).to be(false)
           expect(current_path).to eq root_path
-          expect(flash).to eq "You are not registered for #{conference.title} anymore!"
+          expect(flash).to eq 'You are not registered for The dog and pony show anymore!'
         end
 
         scenario 'deletion of registration is unsuccessful' do