default result sorting to quiz submission descending

completes #85

app/controllers/admin/result_controller.rb

@@ -10,7 +10,9 @@ module Admin
 
     # TODO: Limit results to the quizzes current_user has access to
     def index
-      @candidates = Candidate.where(completed: true).includes(:recruiter)
+      @candidates = Candidate.where(completed: true)
+                             .includes(:recruiter)
+                             .order(:review_status, completed_at: :desc)
     end
 
     def view

app/controllers/quiz_controller.rb

@@ -35,7 +35,7 @@ class QuizController < ApplicationController
   private
 
     def complete_and_email
-      if current_candidate.update_attributes(completed: true)
+      if current_candidate.update_attributes(completed: true, completed_at: DateTime.current)
         current_candidate.build_reviews
         CandidateMailer.submitted(current_candidate).deliver_later
         RecruiterMailer.candidate_submitted(current_candidate).deliver_later