Update the requirements.txt to include pre-commit

* Add the Chinese and English "Contribute Code" documentations.

* Provide some more detail messages in the documentations

* Add C++ and python style check to travis.  
* Update all C++/python code that violate coding standards.

Fix some typos

* Update README.md

Fix typo in the README python SDK example.

* Fix the typo in readme.cn

docker build -f Dockerfile.demo -t visualdl:demo .
docker run -p 8040:8040 visualdl:demo
docker run -p 8040:8040 -v <YOUR_LOG_DIR>:/scratch_log visualdl:demo

* fix build problem that the first build has no js.
* use for loop to check if frontend file is duplicated
* package_data use *.js *.html to match file

* fix #176

* update version-number
* update build and install doc
* add visit address

* support manylinux build

* modify overlay and offset chart view interplay problem

* resolve frontend fecs problem

* resolve the hover circle problem for histogram

* modify the color of multiple lines in scalar

* adjust the frontend code

* modify san template

* adjust histogramHelper code

* reslove fecs code style problem

* resolve the hover circle problem

* remove debug code

* modify the multiple line color

* fix

* fix lib

* add introduction

* update comment, add onnx, update some image

* add image-gan.png

* simplify image sample usage

* simplify image

* add scratch demo

* add scipy into dependency

* add demo

* update readme

* add better scratch demo

* add more data

* support mannul image

* working on quick start

* quick start english