Gemfile分平台加载gem

Gemfile分平台加载gem

区分平台以便加载不同的web server，象tzinfo-data只适用于windows

# Windows does not include zoneinfo files, so bundle the tzinfo-data gem
if RUBY_PLATFORM=~ /win32|mingw/ 
  gem 'tzinfo-data'
  gem 'thin'
else
  gem 'puma'
end