Be consistent with bundle exec

You need bundle exec for all of the commands, not just items 5 and 6

Author: johnpaulashenfelter

docs/DEVELOPER-ADVANCED.md

@@ -18,9 +18,9 @@ to rails, you are likely much better off with our **[Discourse Vagrant Developer
 ## Before you start Rails
 
 1. `bundle install`
-2. `rake db:migrate`
-3. `rake db:test:prepare`
-4. `rake db:seed_fu`
+2. `bundle exec rake db:migrate`
+3. `bundle exec rake db:test:prepare`
+4. `bundle exec rake db:seed_fu`
 5. Try running the specs: `bundle exec rake autospec`
 6. `bundle exec rails server`