Note: Henshin requires at least Ruby 1.9.3
Install the gem with,
$ gem install henshin
then create a site called "my-site" with,
$ henshin new my-site
and view the site with,
$ henshin view my-site
Henshin rebuilds pages when requested, so edit my-site/index.html.slim
and reload the page to see your changes.
Magic!