Put include package data in MANIFEST.in

Instead of use package_data in setup.py, put the files to be
included in MANIFEST.in, and also include a rule to exclude all
the backup files from the package (those with ~ at the end)
Include inve script in MANIFEST.in
Merge pull request #27 from jlesquembre/add_manifest

Put include package data in MANIFEST.in and avoid backup files (*~) in python package