yapf checked

The condition that max length of hist_item_seq[batch_size][i] == 1 is not covered. But it is happened when I run the baseline of dien model.

yapf check

 Neg item and neg cat should be paried

* update readme

* change readme

* change some fuzzy describe

* change

* add some notes
Co-authored-by: Ntangwei12 <tangwei12@baidu.com>
Co-authored-by: Nwuzhihua <35824027+fuyinno4@users.noreply.github.com>

* add save model for step

* add PS/Collective support , add definition in yaml.md

* add check for QueueDataset while saving by step, modify dnn config yaml as an example

* add logging about model save operation

* fix bug for adding check for QueueDataset, modify dnn config yaml

* fix bug for dnn model config yaml

* fix bug for checking QueueDataset

* fix UT fail

* fix UT fail
Co-authored-by: Ntangwei12 <tangwei12@baidu.com>

* add fine tuning trainer

* add doc

* fix
Co-authored-by: NseiriosPlus <tangwei12@baidu.com>
Co-authored-by: Nwuzhihua <35824027+fuyinno4@users.noreply.github.com>

* fix error ASCII

* fix doc error, delete custer reader md

* fix setup.py

* fix install/readme

* fix listwise

* fix travis

* fix readme
Co-authored-by: NseiriosPlus <tangwei12@baidu.com>

* fix readme.md

* fix README.md

* fix README.md

* fix readme

* fix readme

* fix

* fix widedeeep
Co-authored-by: Noverlordmax <515704170@qq.com>
Co-authored-by: Ntangwei12 <tangwei12@baidu.com>

* update

* fix

* delete ps-memory

* fix

* fix

* add cluster support

* add rank model BST

* update readme

* fix AutoInt

* bug fix

* add dien in rank models

* update readme