Add draft release notes for 0.8.12

Review Request #6488 — Created Oct. 21, 2014 and submitted — Latest diff uploaded

Information

Djblets
release-0.8.x
483aadb...

Reviewers

This adds release notes containing all of the changes since 0.8.11. This also
fixes an error in the 0.8.10 release notes that was breaking the index page.

Built and reviewed HTML docs.