Add release notes for 2.0 RC 3.

Review Request #5758 — Created April 30, 2014 and submitted — Latest diff uploaded

Information

Review Board
release-2.0.x
badcbda...

Reviewers

This covers all the fixes and improvements made in 2.0 RC 3. There's a
number of bug fixes, performance improvements, extensibility
improvements, and a couple experimental Web Hook additions in here.

Built the docs and saw them.