Add custom install and Knative codelab links (#720)

* Add custom install and Knative codelab links

* remove custom install 

forgot that https://github.com/knative/docs/pull/565/files exists

* remove colon

Author: RichieEscarez

install/README.md

@@ -48,6 +48,9 @@ Now you're ready to deploy an app:
 
 - View the available [sample apps](../serving/samples) and deploy one of your
   choosing.
+  
+- Walk through the Google codelab, 
+  [Using Knative to deploy serverless applications to Kubernetes](https://codelabs.developers.google.com/codelabs/knative-intro/#0).
 
 ## Configuring Knative Serving