Eager executation

[rzu512]

When I try to scale up my model, I find that tf.scan uses too much memory. Probably I have to use eager execution.

How well does HMC and SGMCMC work with eager execution and tensorflow 2.0?

[thjashin]

That's in our plan but need quite amount of work to switch to the new-style of variable keeping mechanism.

[thjashin]

Welcome for contribution!