Extract from the documentation pages from the repo. developer-tools to be an independant repo.
Those static documentation pages are generated by middleman, you may find more information at [Middleman: Installation] (https://middlemanapp.com/basics/install/).
Only middleman command you need to know is middleman build, it will generate the static pages in the build folder.
You may use the shortcut make to execute middleman build or make clean to remove the folder build