Moved EXIT constants to Xylophone

Signed-off-by: Darren Hill <dchill42@gmail.com>
Made header status codes public

Signed-off-by: Darren Hill <dchill42@gmail.com>
Expanded ExitException to carry header info

Signed-off-by: Darren Hill <dchill42@gmail.com>
Retooled Exceptions

Signed-off-by: Darren Hill <dchill42@gmail.com>
Comment cleanup

Signed-off-by: Darren Hill <dchill42@gmail.com>
Added ExitExceptionTest

Signed-off-by: Darren Hill <dchill42@gmail.com>
Added ExceptionsTest

Signed-off-by: Darren Hill <dchill42@gmail.com>