Log Message:
Updated to 2.1.5. Added license.

ChangeLog:
Added 2008, 2009 to --license statement
Allow numeric parameter immediately after -p or -b
Enforce parameter after -p, -b, -s, before other options
Enforce numeric parameters to have only numeric digits
Try to determine the number of processors for -p default
Fix --suffix short option to be -S to match gzip [Bloch]
Decompress if executable named "unpigz" [Amundsen]
Add a little bit of testing to Makefile