This follows commits 80f4487 and 01399fa; original patch had to be
reverted because it wasn't Python 2.6 compatible and we need it to
be in order to build docs on the djangoproject.com server.
This fix should be replaced by @lru_cache as soon as we drop
Python 2.6 compatibility.
Thanks Florian Apolloner for the review and Alexander Schepanovski
for the original patch.
This reverts commit 80f4487 temporarily, because that commit prevented
the djangoproject.com server from building the docs, because it still
uses Python 2.6.
The reason for this was that git show included the whole changeset in
the output, but only the UTC timestamp was needed. By using git log
it is possible to get just the timestamp. The whole changeset can be
large, and can cause unicode encoding errors.
Moved everything except VERSION and a get_version() stub out of the top-level __init__.py, so that we're not importing all that stuff all the time. And because it's cleaner.