Theme is WordPress 4.0 compatible as of Version 1.5.
To upgrade to WordPress 4.0 you can follow the following steps:
1- Backup your Database
2- Backup your WordPress root directory
3- Download Circle Flip current Version 1.6 from http://themeforest.net/item/circle-flip-responsive-multipurpose-theme/8107961
4- Upload the new theme folder to your wp-content/themes/ replacing your old theme folder and files
5- log in your dashboard and upgrade wordpress.