Make sure you have Ruby 2.3.1 installed. You can install and switch to different versions or Ruby using something like chruby and ruby-install. This project has a .ruby-version dotfile that ensures the switch automatically.
gem install middleman
npm install -g gulp-cli
npm install
middleman serve
And visit http://localhost:9000/
JS
gulp js-lint
And for the gulpfile:
gulp gulpfile-lint
SCSS
gulp sass-lint
or the alias
gulp scss-lint
HTML
gulp html-lint
middleman build
gulp post-build
Static build now at /build