Create README.md for Release VisualDL (#503)

docs/release/README.md

+# Release VisualDL to Pypi
+
+To release VisualDL so that user can do `pip install --upgrade visualdl`, we need to upload the package to pypi.
+
+## Prepare for release build
+
+Make sure update `VERSION_NUMBER` and update new changes in RELEASE.md before starting building.
+
+We support python2.7 and python3.6, here is the pypi link to show what pip packages we have: https://pypi.org/simple/visualdl/
+
+Make sure `build` folder is removed everytime you start building. Following build instructions are assuming you are in MacOS environment:
+
+## Build for MacOS
+In VisualDL root path, run `python setup.py bdist_wheel`.
+After built successfully you will see something like `visualdl-1.2.0-cp27-cp27m-macosx_10_6_x86_64.whl` in `dist` folder.
+'cp27' means python version 2.7, macosx_10_6 means it support mac OS 10.6 and above.
+
+Make sure we build for python2.7 and python3.6, use anaconda to create python version envrionment easily.
+
+## Build for manylinux
+To build for manylinux package, you need a manylinux docker image, please look at details in
+https://github.com/PaddlePaddle/VisualDL/blob/develop/docs/release/build_manylinux.md
+
+## Build for Windows
+To build for windows, you need to have a windows machine and run `python setup.py bdist_wheel` as similar in building for MacOS.
+
+## Upload the wheel package
+Before uploading, make sure you test the package that you generated in dist folder by
+`pip install --upgrade xx.whl` and run `visualdl` to make sure everything is fine.
+
+Before upload to the final pypi website, you can first upload it to a test repo `https://testpypi.python.org/pypi` and test the installation process.
+```shell
+twine upload --repository-url https://test.pypi.org/legacy/ visualdl-*xx.whl
+pip install --index-url https://test.pypi.org/simple/ your-package
+```
+
+Use twine to upload the package to pypi.
+```shell
+twine upload xx.whl
+```