update MANIFEST.in
add remainder of libz libs
Merge pull request #374 from ged-lab/fix/manifest

fix zlib via MANIFEST.in & setup.py
Remove argparse from the requirements

unless it isn't available. Argparse is bundled with Python 2.7+.
This simplifies the installation instructions. Tested with cpython 2.6
& 2.7 on Ubuntu 13.10.