* format the codebase with yapf

* add yapf to travis

* Reformat use yapf 0.27.0

* Add yapf style file

* add tool to analyze log

* minor fix

* plot multi keys, use subparser, modify code

* add two method add_plot_parser and add_time_parser, minor fix

* minor fix

* move add parser func outside main

* move subparser.add inside add parser func