Port rbtools release notes from Review Board repo
Review Request #3964 — Created March 12, 2013 and submitted
Port rbtools release notes from Review Board repo Introduces a releasenotes sphinx configuration, and includes all previous release notes from the Review Board tree. Also, Move the rbtools documentation into a subdirectory under the docs directory. This was done to allow for other sphinx docs configurations such as releasenotes. I have also assigned the documentation copyright to Beanbag, Inc.
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