sculpin publish.sh to github pages

publish.sh

#!/bin/bash

if [ $# -ne 1 ]; then
    echo "usage: ./publish.sh \"commit message\""
    exit 1;
fi

vendor/bin/sculpin generate --env=prod
if [ $? -ne 0 ]; then echo "Could not generate the site"; exit 1; fi

git add -f output_prod && git commit -m "$1"
git subtree push --prefix output_prod origin master