Add release notes for Review Board 2.0.20.
Review Request #7624 — Created Sept. 13, 2015 and submitted — Latest diff uploaded
These cover all the e-mail, diff viewer, file attachment, etc. fixes that have gone into this release. It also contains a variation on the prior security announcement, instructing people on how to install Django 1.6.11.1.
Built the docs and read through them.