Add url helpers & specs for offline participation forms

#5

app/controllers/contests_controller.rb

@@ -192,7 +192,7 @@ class ContestsController < ApplicationController
     @offline.contest = @contest
     @offline.start_time = Time.now()
     if @offline.save
-      redirect_to "/public/#{@contest.friendly_id}/offline/#{@offline.generate_token_for(:token)}"
+      redirect_to offline_form_edit_path(@contest, @offline)
     else
       render :offline_new, status: :unprocessable_entity
     end
@@ -242,7 +242,7 @@ class ContestsController < ApplicationController
                           remaining_pieces: @offline.remaining_pieces)
         extend_completions!(contestant)
       end
-      redirect_to "/public/#{@contest.friendly_id}/offline/#{@offline.generate_token_for(:token)}/completed"
+      redirect_to offline_form_completed_path(@contest, @offline)
     else
       render :offline_edit, status: :unprocessable_entity
     end