Use Sinatra modular application

nikoli.rb

@@ -1,6 +1,6 @@
 #!/usr/bin/env ruby
 
-require 'sinatra'
+require 'sinatra/base'
 require 'sinatra/content_for'
 require 'sinatra/json'
 
@@ -9,6 +9,7 @@ require 'coffee-script'
 require 'slim'
 require 'sass'
 
+class Nikoli < Sinatra::Application
   GAMES = %i{akari hitori nurikabe sudoku}
 
   set :data_folder, File.expand_path('./data')
@@ -38,3 +39,6 @@ get "/data/:game/:file.json" do |game, file|
     data = YAML.load_file(data_file)['data']
     json Array(data).sample
   end
+
+  run! if app_file == $0
+end