Jinoo

Add ignore_key_func

1

### Summary This PR intends to add the functionality to ignore any key within any depth of the hierarchy via passing a callable that returns a boolean to determine whether...

Make log_step_count_steps and save_summary_steps gin configurable for configurable logging frequency.

Fix running transformer in TPU v2-8

3

Ran training successfully on TPU v2-8 TPU software version: nightly. Ran this with tensorflow 1.15