A first pass at What's New document.
Merge remote-tracking branch 'refs/remotes/origin/master' into release-caveats-300

Conflicts:
	docs/index.rst
Experiment to see if GitHub resolves include directives.
Guess includes won't work.
Don't say "orchestration".
Don't say orchestration, move what's new further down since it's less important.
Delete no longer needed text.
Add back missing line.
Address review comment: Better intro phrasing.
Address review comment: It's all new.
Merge pull request #356 from ClusterHQ/release-caveats-300

A What's New document.

Fixes #300.