Trails Aded and High Score Board Fixed

While I was happy with the core gameplay of Chalkroids, I've always felt that the balance was a bit off, especially after the last update, and that the high score board could be improved.  I've fixed a number of outstanding bugs and polished up a lot of the gameplay.  I think the game is now more engaging and better balanced.  Here's what I added and corrected.

Bug Fixes:

• The free ship bug has been fixed.  Bonus ships are now awarded correctly, although at a different rate.
• The sorting of the high score board has been fixed.

Added Features:

• The player ship and bullets now leave a short trail to enhance the gameplay visuals.
• A level indicator has been added in the upper left.  This both balances the UI display and allows the player to keep track on which wave of rocks they're currently on.
• Control inputs for the XBox 360 controller has been added.  Most game controllers will also map correctly, but your mileage may vary.
• The Main Menu screen has been cleaned up and a legend for gamepad controls have been added.  
• The player is now not asked for their initials until after the game is over and then only if they make the top ten scores.

To-Do List:

• Add customizable control mapping allowing players to assign control buttons and input as they prefer.
• Continue game balancing.
• Add player ship power-ups.