v23

* Fix Attribute Error (Jui Pradhan),
* Add screenshots of solutions for all levels (Jui Pradhan),
* Fix Undefined name error for function calls (Jui Pradhan),
* Fix variable and function names (Jui Pradhan),
* Remove unused imports (Jui Pradhan),
* Fix Python3 port regressions (Jui Pradhan),
* Port to Python3 (Srevin Saju),
* Add and update README.md (Ayush Nawal, Steven Higgins, James Cameron),
* Port from GObject to GLib (Tonatiuh Garcia),
* Port to Gtk+3 (Yash Agrawal),
* Fix license and activity metadata (Yash Agrawal),
* Added COPYING and changed metadata (Sidhant Bhavnani)

v1
* Initial Release
