doc building broken due to version strings

[Steven Hardy]

Building docs fails:

# make html
sphinx-build -b html -d build/doctrees source build/html
Making output directory...
Running Sphinx v1.1.3

Exception occurred:
  File "/home/shardy/git/heat/doc/source/conf.py", line 56, in <module>
    release = heat_version.version_string()
AttributeError: 'module' object has no attribute 'version_string'
The full traceback has been saved in /tmp/sphinx-err-KTWYnN.log, if you want to report the issue to the developers.
Please also report this if it was a user error, so that a better error message can be provided next time.
Either send bugs to the mailing list at <http://groups.google.com/group/sphinx-dev/>,
or report them in the tracker at <http://bitbucket.org/birkenfeld/sphinx/issues/>. Thanks!
make: *** [html] Error 1

Fix is to update the doc/source/conf.py file to use the new openstack common VersionInfo methods

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/21110

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/21110
Committed: http://github.com/openstack/heat/commit/a43fcaab7b953b7712f395c51c5db69b8b3089b3
Submitter: Jenkins
Branch: master

commit a43fcaab7b953b7712f395c51c5db69b8b3089b3
Author: Steven Hardy <email address hidden>
Date: Mon Feb 4 14:23:07 2013 +0000

    heat docs : Fix version string issue

    Fix issue with release/version strings in doc build config
    which was causing doc builds to fail with an error.

    Fixes bug 1115269

    Change-Id: Ia02d52f502d808d758a541e84056d5ac94aff8b8
    Signed-off-by: Steven Hardy <email address hidden>