Add 'tox' testing for Python 3.3.

svn merge -r127104:127105 svn+ssh://svn.zope.org/repos/main/transaction/branches/chrism-fix.nonretryablecommitexceptions

Instead, use (only) the 'zope.interface.implementer' class decorator.

- Runs 'setup.py develop' plus installs 'nose' and 'coverage'.

Add 'setup.py docs' alias:

- Installs 'Sphinx' and dependencies.

vb; add trove classifiers for python versions; adjust readme content; add version description to changes.txt

svn merge -r122935:123061 svn+ssh://svn.zope.org/repos/main/transaction/branches/chrism-py3

  and add test.

  objects after calling ``sys.exc_info()`` to get one, causing
  potential reference leakages.

manager. This fixed:

When threads were reused, transaction data could leak accross them,
  causing subtle application bugs.

https://bugs.launchpad.net/zodb/+bug/239086

- Transaction managers and the transaction module can be used with the
  with statement to define transaction boundaries, as in::

with transaction:
         ... do some things ...

See transaction/tests/convenience.txt for more details.

- There is a new iterator function that automates dealing with
  transient errors (such as ZODB confict errors). For example, in::

for attempt in transaction.attempts(5):
         with attempt:
             ... do some things ..

If the work being done raises transient errors, the transaction will
  be retried up to 5 times.

See transaction/tests/convenience.txt for more details.

* Fixed a bug that caused extra commit calls to be made on data
  managers under certain special circumstances.

https://mail.zope.org/pipermail/zodb-dev/2010-May/013329.html

Don't use $Id$.

it makes doing smarter formatting harder.

See LP #142464.