Remove the GosuGUI::Settings module and leave the constants in GosuGUI
Rename the `settings` file to `constants`
Revert to using the Settings module
Finish GosuGUI::Settings documentation
Document GosuGUI's class methods and add description for GosuGUI
Document the GosuGUI::ZOrder module
Fix references to classes from other modules in the documentation
Document GosuGUI::Animation
Add current_frame reader to Animation and #advance return undefined
Document Renderers::ParallaxBackground