Implement final round of review comments from @DouweM.

Refactor the EE::User module

app/models/ee/user.rb

@@ -17,13 +17,11 @@ module EE
     end
 
     def access_level=(new_level)
-      new_level = new_level.to_sym
-      return unless [:admin, :auditor, :regular].include?(new_level)
+      new_level = new_level.to_s
+      return unless %w(admin auditor regular).include?(new_level)
 
-      self.admin = self.auditor = false
-
-      self.admin = true if new_level == :admin
-      self.auditor = true if new_level == :auditor
+      self.admin = (new_level == 'admin')
+      self.auditor = (new_level == 'auditor')
     end
   end
 end