message: Update README.md
  change public_ip to nginx_public_ip in README.md
diff: @@ -89,14 +89,14 @@ can be composed into a higher-level, reusable abstraction.
  1. Get the IP address of the newly-created instance from the stack's outputs:
  ```bash
  - $ pulumi stack output public_ip
  + $ pulumi stack output nginx_public_ip
  13.64.196.146
  ```
  1. Check to see that your server is now running:
  ```bash
  - $ curl http://$(pulumi stack output public_ip)
  + $ curl http://$(pulumi stack output nginx_public_ip)
  Powered by Pulumi!
  ```
  @@ -121,7 +121,7 @@ can be composed into a higher-level, reusable abstraction.
  Outputs:
  - network : "demo-7a734d7"
  - - public_ip: "34.66.58.210"
  + - nginx_public_ip: "34.66.58.210"
  Resources:
  - 11 to delete
  @@ -143,7 +143,7 @@ can be composed into a higher-level, reusable abstraction.
  Outputs:
  - network : "demo-7a734d7"
  - - public_ip: "34.66.58.210"
  + - nginx_public_ip: "34.66.58.210"
  Resources:
  - 11 deleted
  