update localisations
    po/mat-gui.pot
    po/*.po

update changelog:
    git log -> CHANGELOG

update version number:
    lib/mat.py -> __version__ = $VERSION

commit release changes
    git commit CHANGELOG lib/mat.py

create a tag
    git tag -s $VERSION

push the tag
    git push --tags

archive's creation :
    git archive --format=tar.gz --prefix=mat-$VERSION/ $VERSION > mat-$VERSION.tar.gz

signing:
    gpg --armor --detach-sign mat-$VERSION.tar.gz

upload:
    https://mat.boum.org/files

add changelog
    https://mat.boum.org/