fix the sendfile method and use the partial hijacking rack api
config can now be stored in the Staticd::Config singleton class and be available anywhere in the app, rack app and middleware are more independant and configured when initialized, datastore is now initialized outside of the api class and the config.ru is now optionnal and for compatibility only
rebuild Procfile to use the default heroku config names
fix app.json
add the --host option to specify an address to listen to and add the port to the generated url if not 80
fix the ping test using correct port (instead of always using port 80)
fix Rakefile
fix rackup and procfile environment variables
fix welcome and setup page with real node endpoint