Port Tensorflow STS Example to PyMC

[jessegrabowski]

Tensorflow probability has a nice example/explainer about structural time series here.

We should port this over to PyMC using statespace and add it to our example gallery.

[AlexAndorra]

Agreed. Happy to work on that. Although maybe our Berlin tutorial will be demo-ing the same concepts?

[jessegrabowski]

Sure, but I want a 1-to-1 translation, since this is a well-known package. It also serves to benchmark us against the tensorflow implementation.