Support TF models online predictions with TF Serving

[jlewi]

With fairing we'd like to be able to predict locally within the notebook.

For example

model=Model()
model.predict(...)

We need to figure out the exact syntax and model signatures.

For example do we use TF.Example protos?

[r2d4]

/assign @r2d4

[karthikv2k]

Right now users can do arbitrary python predict function which supports TF models but it is not an efficient method. Ref: https://github.com/kubeflow/fairing/tree/master/examples/prediction

This issue is specially for using TF serving for TF models in SavedModel format.

[karthikv2k]

This will be fixed once KFServing support is fully done. Related: #299

[jtfogarty]

/kind feature