message: fix ref to yeoman
diff: @@ -24,7 +24,7 @@ Want to dive right in? [Remix one of our starter kits on Glitch](https://glitch.
  The best way to get started locally with Botkit is by installing our command line tool, and using it to create a new Botkit project. This will install and configure a starter kit for you!
  ```
  -npm install -g yeoman generator-botkit
  +npm install -g yo generator-botkit
  yo botkit
  ```
  