Add a section to the docs about automated code review.

Review Request #9328 — Created Oct. 25, 2017 and submitted — Latest diff uploaded

Information

Review Board
release-3.0.x
c598243...

Reviewers

This currently has a quick description of what status updates are
(including a screenshot of some Review Bot output), and links to the
docs for the CircleCI and Travis CI integrations. In the future we'll
also be able to add docs for Review Bot here.

Built HTML and checked the output.