Sort by recently used icons
Implement test for FontAwesome.load_config
Implement test for FontAwesome.save_config_of_recent_icons
Fix test for FontAwesome.load_config
Refactor tests
Implement test for FontAwesome#sort_by_recent_icons
Add test for FontAwesome.load_config
Add test for FontAwesome.save_config_of_recent_icons
Remove unnecessary attr_reader