Fix dev user seed: multiple ID was used twice.

db/fixtures/development/05_users.rb

@@ -14,10 +14,11 @@
     end
   end
 
+  total = User.count
   (1..5).each do |i|
     begin
       User.seed(:id, [
-        id: i + 10,
+        id: total + i,
         username: "user#{i}",
         name: "User #{i}",
         email: "user#{i}@example.com",