Added silent: true flag for backbone set method in reorder questions
Optimised the deletion of questions in survey builder
Setup memcache on engineyard
Since memcache servers are stored under 'defaults', it should not fetch current environment's value from hash.
Fixed a bug when order_number were not updated after re-rendering
Fixed category's sub questions to update it's order number when destroyed
Fixed a bug where sub-questions question_number wasn't updated after deleting/reordering a question