Version 0.6 - New look

Added a new look to the main game and added music, cleaned up the settings page. Maybe some changes to the way game over is triggered and add a box lid to indicate  impending game over state.

Main issues fixed:

• Pop particules now position themselves correctly
• Sounds sliders now work correctly
• Workaround (popping animals) when they get pushed out of the box
• Cleaned up audio issues with animal to animal contact, reducing the amount of noise occurring when there's lots going on, or the group are settling
• Chain messages now update as the chain number increases if it's too soon to bring up another chain message.
• Fixed elephant not popping during game over