Fix relative requires

This lets us run the code from anywhere by specifying the path to
PuppetMaster.php.
Replace integer exit codes with proper exceptions
Reorganize code to use PSR-0

I've refactored a bit to take advantage of PSR-0 autoloading
(http://www.php-fig.org/psr/psr-0/).

This is much neater in general, but I'm not happy with how Game/Utils
and Game/System/Exceptions work:

1. It doesn't seem we can call Game/Utils/initWithVar simply by
   importing Game/Utils. PHP tries to autoload initWithVar from the
   current namespace.

2. Using PSR-0, classes need to be split into their own files. This
   leads to a lot of clutter for empty named exceptions.