chore: Makefile, gulpfile, index.ls

* let gulpfile only active in non-production environment
* use standard nodejs script in production
fix(server/config): remove unused middlewares
docs(README.md): update description
fix(server/index): remove res.bootstraping
chore(Makefile): clean before release
chore(server/config): use DATABASE_URL directly
fix(IndexCtrl): make exprs optional
chore(views/footer): add authors