Merge branch 'develop' into gilbert-ext4

Merge branch 'develop' into gilbert-ext4

* develop:
  Fixed a few bugs with the documentation, and links to the documentation from the README. Sphinx can now build the documentation reliably due to conf.py explicitly adding the docs directory to the path. Added a link to the Bitbucket mirror, extending the set currently consisting of GitHub and Gitorious.
  Bumped version number and wrote release notes for 0.9.2 in preparation for release.
  Fixed an exception with JSONAttributes using DateField or DateTimeField as their field template when the stored value is None. Fixes #178.
  Updated copyright date range to end in 2012 instead of 2011.