middleman-typogruby

Add this to your Gemfile:

gem 'middleman-typogruby', :git => "git://github.com/ssbx/middleman-typogruby.git"

And this to your config.rb (these are the default options):

activate :typogruby do |typo|
    typo.entities = false
    typo.typeamp = true
    typo.caps = true
    typo.initial_quotes = true
    typo.smartypants = true
    typo.widont = true
end

See Typogruby doc for documentation.