Merge pull request #575: Import 2.7.0 release docs

Import 2.7.0 release docs
tree: b140964460edaf3a8c3045b5875c55c3f72584f0
  1. javadoc/
  2. pydoc/
  3. .gitattributes
  4. README.md
README.md

This branch contains the generated release documentation for http://beam.apache.org.

To contribute to the website, please modify the website sources in apache/beam. See the contribution guide for details.

To add release documentation for a new release, see the release guide.