Fixing setup file to automatically look for packages. Previously, it was failing to pickup the package 'pyxva.cmd' which would need to be included.

Signed-off-by: Rob Dobson <rob@rdobson.co.uk>
Merge pull request #10 from rdobson/find_packages

Fixing setup file to automatically look for packages.
Chopper - sparse chop a stream to chunks

Based on the original mkxva script, and on the documentation here:
http://wiki.xenproject.org/wiki/Disk_import/export#VM_import.2Fexport
slicing a stream to chunks, discarding the zeroes, always keeping the
first and the last element.