Add kfserving examples

[Jeffwan]

• It would be great to use AWS S3 to host sample models
• Add Instructions to install knative and kfserving
• One general example using S3
• One SDK example - Create inference using sdk.
• One e2e examples -> with fairing or basic mnist training

[Jeffwan]

Let's use original model from gcs now. Once we can public S3, we move model there