* fix checkpoint naming + trial id for non-ray mode, fix the bug in running test mode, delete all the checkpoints in non-ray mode
* finished testing for checkpoint naming, delete checkpoint, ray, max iter = 1
* adding predict_proba, address PR 293's comments
close#293#291
* api doc for chacha
* update params
* link to paper
* update dataset id
Co-authored-by: Chi Wang (MSR) <chiw@microsoft.com>
Co-authored-by: Qingyun Wu <qiw@microsoft.com>