Update MANIFEST.in
Update MANIFEST.in

post_install.py added

Former-commit-id: f4d47fb5833092c21a4079a300d7efa65c209bdf
gsarma/PyOpenWorm,kaustubhcs/PyOpenWorm,openworm/PyOpenWorm,openworm/PyOpenWorm,gsarma/PyOpenWorm,travs/PyOpenWorm,hnunner/PyOpenWorm