Alternative to `jekyll --server`. Need to run `jekyll --auto` in adjacent terminal for reloading.

jekyll-rack

require 'bundler/setup'
require 'rack/contrib/try_static'

use Rack::TryStatic, :root => "_site", :urls => %w[/], :try => ['.html', 'index.html', '/index.html']
run Proc.new {|env| [404, {"Content-Type" => "text/plain"}, ["File not found"]]}