You can uninstall or removes an installed atari800 package itself from Ubuntu 16.10 (Yakkety Yak) through the terminal,
$ sudo apt-get remove atari800
If you would like to remove atari800 and it's dependent packages which are no longer needed from Ubuntu,
$ sudo apt-get remove --auto-remove atari800
If you use with purge options to atari800 package all the configuration and dependent packages will be removed.
$ sudo apt-get purge atari800
If you use purge options along with auto remove, will be removed everything regarding the package, It's really useful when you want to reinstall again.
$ sudo apt-get purge --auto-remove atari800