Nesta is a lightweight Content Management System, written in Ruby using the Sinatra web framework. Nesta has the simplicity of a static site generator, but (being a fully fledged Rack application) allows you to serve dynamic content on demand. Content is stored on disk in plain text files (there is no database). Edit your content in a text editor and keep it under version control (most people use git, but any version control system will do fine). Implementing your site's design is easy, but Nesta also has a small selection of themes to choose from.
Gemfile gem 'nesta', '~> 0.9.1'
install gem install nesta -v 0.9.1