v2.2.0

• Adds option to scaffold apps with --template={name} to use named Probot templates
• Adds --typescript option which aliases to --template=typescript to allow scaffolding using a default typescript template
• Update README with instructions for using this with npm > 6
  • You can now invoke this without having to install create-probot-app globally by typing npm init probot-app [--typescript] my-probot-app