Completed sound implementation to fix #12
Implemented returning to overworld to fix #11
Created stat panel for showing current stats
Fixed stat transparency issues to fix #10
Updated README.md to talk about the project page
Fixed bad link in README.md
Made GUI repaint after switching windows

Fixes #23 and #19
Ensured options are set to fix #21
Added an SFX test button to the options screen
Fixed audio volume not adjusting to fix #20
Made BGM loop to fix #22
Updated Screen API

- Made all screen listeners extend ScreenListener.
- Added listener functionality directly to Screen.
Made ScreenListeners properly extend superclass
Updated GraphicalInterface to use new Screen API

- Auto-removed GraphicalInteface as a listener from the
previously-displayed screen when the screen is switched.
Fixed #24

- Added auto-healing after each battle.
Changed listener API to be more abstract

- Moved Listener methods into their own interface.
- Renamed GameMenu and GameMenuBar to Menu and MenuBar.
- Added Listener API support to menu classes.
Added Listener API to MenuBar.
Added menu response methods
Finished making menus respond

Fixes #17, fixes #16, fixes #15, and fixes #14
Added MP3 playing

- Note that this requires restructuring the build script.